The Thailand-Cambodia Border Crisis is ASEAN’s Moment of Truth

As deadly clashes escalated and spread along the Thailand–Cambodia border starting 24 July, ASEAN again confronts a crisis that shows up its institutional limitations. What began as a localised dispute over troop movements near ancient temples has escalated into a full-blown conflict, with over 30 lives lost, tens of thousands displaced on both sides of the border, and both governments trading accusations of aggression.

Thus far, ASEAN has done what it often does in initial phases of intra-regional conflict: nothing. There has been no official statement by the grouping although Malaysia’s Prime Minister Anwar Ibrahim has reportedly spoken with Cambodia’s Prime Minister (PM) Hun Manet and Thailand’s acting premier Phumtham Wechayachai and will today host ceasefire talks in Kuala Lumpur. Notably, US officials are present to support the dialogue and China is also participating, underscoring growing international concern and the high stakes involved. Yet ASEAN remains paralysed by its founding principles of non-interference and consensus, and even a basic statement calling for restraint is unlikely, as it would require all ten members to agree on its wording.  

ASEAN does have limited tools at its disposal. The Treaty of Amity and Cooperation (TAC) — which embodies universal principles of coexistence and friendly cooperation — includes a High Council designed for mediation, conciliation, and inquiry. However, that mechanism has never been activated: not for Myanmar, nor during earlier Thai-Cambodian clashes over the disputed Preah Vihear temple in 2008–2011, and not now. Again, this is because ASEAN operates by political consensus, not institutional autonomy. Without a mandate from all ten member states, ASEAN cannot act, no matter how urgent the crisis. This continued inaction, when two member states are on the brink of war, may render the TAC not just dormant but dangerously close to irrelevance.

The latest conflict shows how fragile ASEAN’s peace framework is. Informal norms and quiet diplomacy are no match for member states trading artillery fire. Worse, ASEAN’s inaction is now a pattern, not an exception. For years, the bloc has failed to produce meaningful results in addressing the Myanmar crisis, despite countless high-level meetings, the “Five-Point Consensus” and statements, and the appointment of multiple envoys. On the South China Sea, it remains divided, with no unified position or credible mechanism to deter grey-zone coercion or militarisation. In all these cases, the gap between ASEAN’s rhetoric and its reality continues to widen.

Public confidence in ASEAN is slipping. According to ISEAS – Yusof Ishak Institute’s State of Southeast Asia 2025 Survey, 35 per cent of respondents across the region believe ASEAN is “too slow and ineffective” in dealing with fast-moving challenges, and risks becoming irrelevant.

If ASEAN cannot address a military crisis within its own neighbourhood, its claims to regional centrality and leadership will ring hollow. The parties to the current crisis seem bellicose despite the prospect of today’s talks. Cambodia issued a blistering statement through its Ministry of National Defense, condemning what it described as Thai “military aggression” and invoking its individual right to self-defence under Article 51 of the United Nations (UN) Charter. Thailand has rejected Cambodia’s accusations and reaffirmed its commitment to resolving the matter bilaterally, while warning Cambodia to halt hostilities. Malaysia, as ASEAN Chair, issued a cautious call for restraint and dialogue, while individual members Singapore, Indonesia, the Philippines, Vietnam, Laos, and Brunei have expressed concern through their respective foreign ministries.

If ASEAN cannot even react when two of its members exchange fire, what then is its value as a regional peace and security platform?

These fragmented responses are no substitute for a collective ASEAN position, whether expressed as a consensus or joint statement. This divergence underscores the political fault lines within the grouping. Thailand continues to insist on bilateral mechanisms like the Joint Boundary Commission, which are unlikely to function effectively, especially now that both sides have resorted to arms. Cambodia appears more open to international mediation, having raised the issue at the UN Security Council and signalling its willingness to involve external actors. With both sides entrenched and no ASEAN platform activated, the risk of prolonged violence is real. If left unchecked, this could develop into a broader war.

ASEAN has historically struggled to resolve disputes between its members. For instance, it never intervened directly in the Sabah dispute between Malaysia and the Philippines in 2013 nor in earlier border skirmishes between Thailand and Laos in the 1980s. The 2008–2011 Preah Vihear clashes — which are related to the latest conflict — offer a sobering precedent. Cambodia appealed to ASEAN and Indonesia (then ASEAN Chair in 2011) dispatched observer teams but the effort collapsed when Thailand withdrew support. The matter was eventually brought to the International Court of Justice (ICJ), which in 2013 ruled that Cambodia held sovereignty over the temple promontory and ordered Thai troops to withdraw. The ICJ ruling helped to de-escalate tensions but that the disputing parties turned to the ICJ highlights members’ lack of trust in ASEAN to resolve such conflicts.

Today, ASEAN still has options to break from history, though the window is closing. While Malaysia is leading mediation efforts as ASEAN Chair, other members like Indonesia or Singapore, with their experience in international mediation, could perhaps contribute to sustained dialogue and ceasefire monitoring if needed. The symbolic activation or at least exploration of convening the TAC High Council could show that ASEAN is willing to test its frameworks, even if a political resolution remains distant. Humanitarian corridors and coordinated evacuation efforts could be another immediate entry point for ASEAN to demonstrate relevance.

The risks of continued inaction are high. If ASEAN fails to respond, it creates a vacuum and others may fill it. China, which maintains close ties with Thailand and Cambodia, has expressed interest in supporting stability. If Beijing, the US, or other major powers assume a mediating role in ASEAN’s place or eclipse ASEAN, this will further dilute the bloc’s centrality and reinforce perceptions that ASEAN cannot manage its own members. This crisis is not merely about border disputes or the cultural symbolism of an ancient temple but is a test of ASEAN’s credibility, cohesion, and institutional maturity. If ASEAN cannot even react when two of its members exchange fire, what then is its value as a regional peace and security platform? The fact that meaningful action depends on the initiative of the ASEAN Chair — rather than any institutional mechanism — only deepens concerns about the bloc’s structural weaknesses. The time for quiet diplomacy and procedural caution has passed. ASEAN must act before irrelevance becomes its defining legacy.

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