Abstract

The recrudescence of armed hostilities between Cambodia and Thailand in 2025, manifested in sustained artillery exchanges, aerial bombardment, and reciprocal accusations of sovereignty violations, constitutes a critical juncture for the ASEAN Political-Security Community (APSC). This article contends that ASEAN's circumscribed crisis-management efficacy derives from three mutually reinforcing pathologies: (1) institutional design deficits—specifically, the consensus requirement codified in Article 20 of the ASEAN Charter and the dormancy of the Treaty of Amity and Cooperation's High Council; (2) domestic legitimation imperatives that incentivize nationalist brinkmanship over compromise; and (3) the systemic pressures of intensifying Sino-American strategic competition, which fracture intra-ASEAN cohesion by creating asymmetric external dependencies. Drawing upon neoclassical realist frameworks and Putnam's two-level game logic, the analysis demonstrates that ASEAN's normative architecture—predicated on non-interference and sovereignty—paradoxically undermines its capacity to mediate sovereignty-adjacent disputes. The article concludes by advancing policy prescriptions anchored in conditional institutionalism, arguing that ASEAN must transition from declaratory diplomacy to enforcement-capable mechanisms if regional centrality is to retain operational meaning –.emec+1

1. Introduction: The Return of Interstate Violence and Regional Order

The eruption of large-scale military confrontation along the Thai-Cambodian frontier in July 2025, and its subsequent intensification in December despite Malaysian-brokered ceasefire arrangements, represents the gravest challenge to ASEAN's peace-preserving function since the organization's institutional consolidation,. The violence—characterized by sustained use of heavy artillery, multiple-launch rocket systems, and precision airstrikes—produced not merely tactical casualties but strategic reverberations for regional architecture. As Mearsheimer posits in The Tragedy of Great Power Politics, international institutions are typically unable to constrain state behavior when vital security interests are at stake; states prioritize survival and relative gains over institutional compliance. The 2025 escalation validates this realist skepticism: despite decades of ASEAN socialization and the existence of formal dispute-settlement frameworks under both the ASEAN Charter and the Treaty of Amity and Cooperation (TAC), two member states resorted to kinetic force to prosecute territorial claims –.amro-asia+3

The conflict's genealogy traces to unresolved colonial cartography—specifically, the Franco-Siamese treaties of 1904 and 1907—and the International Court of Justice's 1962 judgment awarding the Preah Vihear temple complex to Cambodia while leaving adjacent borderlands legally ambiguous,. The ICJ's 2013 interpretation ruling, intended to clarify demarcation around the provisional demilitarized zone, failed to eliminate contestation on the ground,. This pattern underscores a structural disjuncture between international legal adjudication and the domestic political incentives that sustain territorial disputes. The resumption of hostilities immediately preceding December 2025 foreign ministerial talks convened under ASEAN's Malaysian Chairmanship illustrates how nationalist imperatives can override even the anticipatory effects of diplomatic engagement,.rsis+5

The scholarly significance of this crisis extends beyond bilateral relations. It presents, as Lin and Martinus aptly characterize, "ASEAN's moment of truth"—a test of whether the organization can translate its declaratory commitment to peaceful settlement into operational crisis management when member states exchange fire. If ASEAN cannot stabilize intra-mural armed conflict, its claims to regional centrality become vulnerable to what Nye terms "institutional irrelevance," where organizations persist in form but lose substantive influence over state behavior.scholarship.law.missouri+1

2. Theoretical Framework: Neoclassical Realism and Domestic Political Transmission Belts

2.1. Analytical Approach

This analysis adopts a neoclassical realist lens, which posits that while systemic pressures (distribution of capabilities, polarity) establish the permissive context for foreign policy, domestic-level variables mediate how these pressures translate into state behavior,. As Rose articulates in "Neoclassical Realism and Theories of Foreign Policy," state responses to external threats are filtered through "unit-level intervening variables"—including elite perceptions, domestic political institutions, and societal pressures. This framework is particularly salient for understanding ASEAN dynamics, where institutional outputs depend fundamentally upon member-state consent and where sovereignty-sensitive issues activate intense domestic audience costs.lowyinstitute+1

Complementing this structural approach, Putnam's "two-level game" framework elucidates why national leaders may sustain hardline positions internationally when domestic ratification constraints narrow the "win-set" of mutually acceptable settlements. In Putnam's formulation, negotiators simultaneously play on two boards: the international bargaining table and the domestic political arena where constituencies must ratify agreements. When domestic constituencies demand uncompromising defense of territorial claims—as nationalist publics in both Cambodia and Thailand have done—leaders face steep political costs for concessions, thereby reducing the overlap between internationally negotiable outcomes and domestically ratifiable positions.moderndiplomacy+1

2.2. Institutional Design and the Consensus Trap

ASEAN's operational paralysis during the 2025 crisis stems proximately from its institutional architecture. Article 20 of the ASEAN Charter mandates that "decision-making in ASEAN shall be based on consultation and consensus," effectively granting each member state a veto over collective action. While this norm has historically enabled solidarity among heterogeneous polities, it transforms into a debilitating constraint during high-intensity disputes involving member states themselves. The TAC's High Council—theoretically designed for mediation, conciliation, and inquiry under Articles 14-17—has never been operationalized, not during the Myanmar crisis, nor during earlier Thai-Cambodian clashes (2008-2011), nor in 2025 –,. As Acharya observes, ASEAN's constitutive norms of non-interference and sovereign equality, while promoting regional cohesion, simultaneously circumscribe the organization's capacity for intrusive conflict management.casebook.icrc+4

The structural deficit is twofold: ex ante preventive capacity and ex post enforcement authority. Despite bilateral mechanisms like the Joint Boundary Committee (JBC) and General Border Committee (GBC), diplomatic engagement in June 2025 produced no substantive de-escalatory commitments. By July, when violence erupted, ASEAN's intervention was purely reactive—convening statements, deploying observer missions with ambiguous mandates, but imposing no binding obligations or graduated sanctions for non-compliance. This reactive posture contrasts sharply with organizations possessing supranational enforcement mechanisms, such as the European Union's ability to condition membership benefits on behavioral compliance.emec

3. Domestic Political Incentives: Legitimacy, Nationalism, and the Two-Level Game

3.1. Cambodia: Dynastic Succession and Strategic Nationalism

Prime Minister Hun Manet's handling of the border crisis must be contextualized within Cambodia's political succession dynamics. Having assumed office in 2023 following his father Hun Sen's prolonged tenure (1985-2023), Manet confronts dual legitimation challenges: consolidating authority within the Cambodian People's Party (CPP) elite structure and projecting decisiveness to nationalist constituencies,. The border conflict furnishes a legitimating platform—what sociologists term the "rally-round-the-flag" effect—enabling Manet to emulate his father's strongman persona while preemptively neutralizing internal critiques of dynastic succession.amro-asia+1

Critically, Cambodia's power structure remains bifurcated: formal constitutional authority vested in Hun Manet coexists with Hun Sen's continued influence as Senate President and CPP elder,. This duality complicates ASEAN's formal mediation channels, as official interlocutors may not command full decision-making authority. Hun Sen's history of inflammatory rhetoric targeting Thai political figures—specifically his public attacks on suspended Prime Minister Paetongtarn Shinawatra—amplifies tensions beyond conventional diplomatic management. From a two-level game perspective, Hun Manet's domestic ratification constraint is stringent: any perceived territorial concession would invite accusations of weakness vis-à-vis his father's legacy, thereby jeopardizing elite cohesion and public legitimacy.specialeurasia+2

3.2. Thailand: Civil-Military Relations and the Sovereignty Cudgel

Thailand's internal fractures manifest differently but with analogous effects. The suspension of Prime Minister Paetongtarn Shinawatra in July 2025—following leaked communications with Hun Sen—created a leadership vacuum exploited by military-royalist factions. The Royal Thai Army has historically leveraged sovereignty disputes to assert institutional prerogatives, framing territorial defense as a non-negotiable military responsibility beyond civilian oversight,. Acting Prime Minister Phumtham Wechayachai leads a fragile Pheu Thai coalition vulnerable to nationalist criticism, rendering any compromise diplomatically and domestically untenable.emec+1

Thailand's insistence on bilateral negotiation frameworks rather than multilateral ASEAN mediation reflects this domestic constraint,. Bilateral mechanisms afford Thai elites greater control over narrative framing and tactical concessions, whereas ASEAN-led processes risk exposing the government to accusations of ceding sovereignty to regional interference. Putnam's model illuminates this logic: the smaller the domestic win-set (the range of internationally negotiated outcomes acceptable domestically), the greater the likelihood of negotiation failure. For both Bangkok and Phnom Penh, nationalist constituencies have effectively narrowed win-sets to near-zero overlap, producing diplomatic deadlock punctuated by military escalation.rsis+2

4. Geopolitical Dimensions: Great Power Competition and Intra-ASEAN Polarization

4.1. Cambodia's Strategic Alignment with China

Phnom Penh's ability to resist regional pressure derives substantially from Chinese diplomatic and material support. Beijing's provision of military aid—including advanced artillery systems and political cover in multilateral forums—furnishes Cambodia with strategic depth to circumvent ASEAN consensus,. From a balance-of-power perspective, small states engage in "bandwagoning" behavior when aligning with rising regional hegemons offers greater security than autonomy or counter-balancing coalitions. Cambodia's close alignment with China exemplifies this logic: Chinese patronage mitigates vulnerability to ASEAN peer pressure while enabling Phnom Penh to function as an effective "veto player" within the bloc on issues affecting Chinese interests (e.g., South China Sea, human rights),.aljazeera+1

4.2. Thailand's Recalibration Toward Washington

Conversely, the conflict incentivizes Thailand to reinvigorate its alliance with the United States, a relationship attenuated in recent years by Bangkok's hedging strategies,. Facing a militarily modernized Cambodia (courtesy of Chinese arms transfers), Thai security planners increasingly interpret U.S. security guarantees through the prism of the border dispute. However, Washington's response has been characterized by bureaucratic incoherence and delayed engagement. The Trump administration's reorganization of the State Department—including dismantling the Office of Multilateral Affairs responsible for ASEAN engagement—has removed institutional expertise critical for rapid crisis response. Secretary of State Marco Rubio's prior criticisms of Cambodia's authoritarian governance, juxtaposed with recent U.S. sanctions on Thai officials over Uyghur deportations, complicate Washington's diplomatic positioning.amro-asia+1

4.3. Strategic Bifurcation and ASEAN's Centrality Deficit

The superimposition of Sino-American competition onto a bilateral territorial dispute transforms the conflict into a potential proxy dimension of great power rivalry. This dynamic threatens to bifurcate ASEAN along geopolitical fault lines, undermining the organization's aspirational "strategic autonomy",. As Lin and Martinus caution, "If ASEAN fails to respond, it creates a vacuum and others may fill it". China's proactive mediation offers, alongside U.S. technical support for ceasefire monitoring (including satellite imagery), signal that external powers are already assuming roles ASEAN has proven unable or unwilling to perform,. This substitution effect erodes ASEAN centrality from functional irrelevance to symbolic obsolescence.emec+3

5. Implications for ASEAN: Normative Erosion, Economic Disintegration, and Institutional Paralysis

5.1. The Collapse of the "ASEAN Way"

The 2025 crisis exposes the practical limitations of the "ASEAN Way"—a normative framework emphasizing non-interference, consensus, and quiet diplomacy. Constructivist scholars have long argued that ASEAN's norms constitute "shared meanings" that shape member-state behavior by defining appropriate conduct. Yet norm effectiveness depends on robust internalization and consistent adherence; when vital interests supersede norm compliance, institutional socialization proves insufficient. The swift collapse of the October 2025 "Kuala Lumpur Declaration"—a peace accord negotiated under Malaysian mediation—demonstrates that ASEAN's norms lack enforcement mechanisms to raise the costs of defection,.amro-asia+3

Pradnyana aptly characterizes ASEAN's role as "a mere observer of peace and not its builder," capturing the organization's reactive posture devoid of proactive stabilization capacity. The inability to operationalize graduated sanctions, deploy peacekeeping forces with coercive mandates, or link security compliance to economic benefits reflects what Keohane terms "institutional weakness"—where organizations lack authority to punish non-cooperation or enforce collective decisions.fpciui+1

5.2. Economic Connectivity and Regional Integration at Risk

The militarization of border zones directly contradicts the objectives of the ASEAN Economic Community (AEC), particularly physical connectivity initiatives. The conflict disrupts the East-West Economic Corridor, a flagship project integrating the Mekong sub-region through cross-border infrastructure,. Trade embargoes, border closures, and the displacement of cross-border labor flows impose economic costs extending beyond the immediate belligerents, affecting regional supply chains and investment climates. Pradnyana argues for "conditional cooperation," wherein ASEAN makes benefits of economic integration contingent upon security compliance, thereby raising political costs for military escalation and creating positive incentives for dispute resolution.alm+2

5.3. Credibility Deficits and Public Confidence

Empirical evidence substantiates declining regional confidence in ASEAN's efficacy. The ISEAS-Yusof Ishak Institute's State of Southeast Asia 2025 Survey reports that 35% of regional respondents consider ASEAN "too slow and ineffective" to address contemporary challenges, with risks of institutional irrelevance. This erosion of public legitimacy compounds elite-level dysfunction: when citizens perceive ASEAN as impotent, domestic constituencies grow skeptical of regional solutions, further empowering nationalist politicians who advocate unilateral action over multilateral engagement.rsis

6. Policy Recommendations: Toward Conditional Institutionalism and Graduated Enforcement

6.1. Operationalizing "ASEAN Minus X" for Crisis Management

To transcend consensus paralysis, ASEAN must adopt flexible geometry mechanisms that permit subsets of member states to undertake collective action without requiring unanimity,. The "ASEAN Minus X" formula—already employed in economic integration contexts—should be extended to security domains. Specifically, a "Border Conflict Protocol" could enable disputing parties to voluntarily opt into enhanced mediation, arbitration, and observer mission frameworks, subject to peer monitoring by non-claimant states. This preserves formal sovereignty while establishing conditional pathways for intrusive conflict management.ethesisarchive.library.tu+1

6.2. Institutionalizing the Extended Troika Mechanism

Current ASEAN crisis response depends excessively on the annual Chair's diplomatic capacity, creating discontinuities in mediation efforts. An extended Troika mechanism—comprising past, present, and future Chairs—would ensure institutional continuity, reduce burden concentration, and insulate mediation from the vagaries of leadership rotation. This permanent crisis-management body, modeled on the African Union's Peace and Security Council architecture, could maintain standing relationships with disputing parties and deploy rapidly during escalatory phases.e-ir

6.3. Conditional Economic Integration: Linking AEC Benefits to Security Compliance

Drawing upon institutional design principles articulated by Keohane and Nye in Power and Interdependence, ASEAN should leverage economic interdependence as a compliance mechanism,. Membership in preferential trade arrangements, access to connectivity funding, and participation in regional value chains should be conditioned upon adherence to peaceful dispute-settlement commitments. This strategy transforms economic integration from a parallel track into a strategic instrument that raises opportunity costs for military escalation while creating positive incentives for diplomatic resolution.silobreaker+2

6.4. Deploying Robust Monitoring and Verification Missions

Current ASEAN observer missions suffer from ambiguous mandates and symbolic deployment. A reformed architecture should establish an ASEAN Border Peace Monitoring Cell with permanent staffing, clear reporting lines to the ASEAN Secretary-General, and authority to trigger high-level review mechanisms upon detecting violations. Drawing upon Lederach's conflict transformation theory, such missions should extend beyond military observation to facilitate cross-border civil society engagement, joint de-mining operations, and community-level trust-building,.papers.ssrn+1

6.5. Strategic Learning from Comparable Regional Organizations

ASEAN can benefit from comparative institutional analysis, particularly examining how the African Union balances sovereignty principles with interventionist capacities through its Responsibility to Protect framework. While wholesale adoption is politically infeasible, selective adaptation—such as peer-review mechanisms and graduated intervention protocols—could enhance ASEAN's conflict-management toolkit without fundamentally compromising non-interference norms.academia

7. Conclusion: ASEAN's Existential Choice

The 2025 Cambodia-Thailand crisis constitutes more than a bilateral territorial dispute; it represents an existential test of ASEAN's institutional raison d'être. Six decades after its founding, ASEAN confronts a stark choice: evolve beyond declaratory diplomacy toward operational crisis management, or accept gradual marginalization as great powers assume conflict-resolution roles the organization cannot perform. The inability to prevent, mediate, or resolve armed conflict between member states fundamentally contradicts ASEAN's constitutive purpose as articulated in the ASEAN Charter—promoting regional peace, security, and stability.casebook.icrc

The pathologies identified—institutional design deficits, domestic political imperatives, and geopolitical polarization—are mutually reinforcing yet individually addressable through targeted reforms. ASEAN need not abandon its normative foundations of non-interference and consensus to enhance effectiveness; rather, it must supplement these norms with conditional institutionalism that permits graduated, consent-based intervention when vital collective interests are threatened. The organization's continued relevance depends upon demonstrating that Southeast Asian regionalism can produce tangible security outcomes, not merely convene dialogues.

As Pradnyana concludes, ASEAN must evolve "from a convenor of conversation to the guarantor of conflict management". Failure to undertake this transformation risks reducing the "ASEAN Community" from an operational framework to what constructivists term a "failed norm"—rhetorically invoked but practically inoperative. The December 2025 resumption of hostilities, despite diplomatic engagement, underscores the urgency of this institutional reckoning. Regional architecture cannot remain static while strategic environments transform; adaptive capacity constitutes the difference between institutional resilience and obsolescence.emec

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The Cambodia-Thailand Border Conflict and ASEAN's Legitimacy Crisis: Structural Constraints, Norm Contestation, and the Limits of Regional Institutionalism