Redefining ASEAN centrality

Last month, Thailand decided to scrap a Memorandum of Understanding with Cambodia (Opens in new window) concerning their maritime disputes, including a framework for a joint marine resources management in the sea with an estimated (Opens in new window) $300 billion worth of energy resources at stake.

In response, Cambodia triggered a dispute resolution process (Opens in new window) under the United Nations Convention on the Law of the Sea (UNCLOS). The mechanism has only been used once before, in 2016 by Australia and Timor-Leste (Opens in new window), allowing the parties to resolve a decades-long maritime dispute in just under two ​years.

The Thailand–Cambodia dispute also has its own long antecedents, and this latest move presents a new chapter. In December 2025, Cambodia formally asked the UN Security Council to take action after border clashes beginning in the middle of the year. While Cambodia has favoured seeking settlement through external mechanisms, Thailand prefers bilateral talks, as Thai Foreign Minister Sihasak Phuangketkeow has stated (Opens in new window).

Under the UNCLOS process, a five-member commission will be formed, with two members from Thailand and two from Cambodia. The four members will jointly select one chairperson, bringing the total to five. The conciliation commission will hear arguments from both sides and consider evidence before proposing a way to end the dispute. Any ruling will be non-binding, even though both countries are signatories to the Convention. This also means that Cambodia is not guaranteed a favourable outcome even if the process succeeds.

What it does guarantee is a formal, internationally recognised process with a defined timeline.

That Cambodia prefers this approach over ASEAN’s consensus process speaks volumes about confidence in regional mechanisms. That should be seen as a regional reality check: ASEAN member states are not fully convinced by the bloc’s mechanisms for intra-bloc disputes.

Neither party consulted ASEAN first as a primary mechanism. ASEAN’s dispute settlement mechanisms principle known as the “ASEAN Way” rests on non-interference and consensus – allowing sovereignty protection but preventing binding resolution. The success of ASEAN as an institution builder has earned it its “centrality (Opens in new window)” in the region. The ASEAN Way is also the bloc’s official anthem.

While emphasising the use of informal practices and norms, the ASEAN Way does not preclude third-party mediation to settle bilateral disputes. Malaysia and Indonesia have done so when deciding to go to the International Court of Justice to settle sovereignty over the islands of Sipadan and Ligitan.

This leaves ASEAN as a platform when useful for member states’ interests – bypassed when it is not. It does not mean that ASEAN should abandon its ASEAN Way or claim to centrality – only that centrality itself needs to be refined.

Instead of claiming the bloc can resolve internal disputes through informality and consensus – a reality exposed by the Cambodia–Thailand pattern – ASEAN should position itself as the coordinating framework through external mechanisms, including UNCLOS, where solutions are implemented and legitimised. In practice, this means ASEAN should be the first call when disputes arise, not to resolve them unilaterally, but to convene the parties, identify appropriate mechanisms, and remain present throughout the process.

When Cambodia triggers UNCLOS, ASEAN should be coordinating alongside it – not watching from the sidelines. ASEAN centrality, in this case, would function as convening authority, not resolution authority.

As Khang Vu noted last year in The Interpreter (Opens in new window), Thailand and Cambodia are close partners of the United States and China respectively, creating a risk of great-power intervention if ASEAN cannot mediate conflict internally. Washington and Beijing already played active roles in a ceasefire (Opens in new window) during a land border conflict between Cambodia and Thailand last year, leaving questions about ASEAN centrality.

While the UNCLOS conciliation between Thailand and Cambodia may take years and produce non-binding recommendations, it also poses a test for ASEAN’s credibility. That test will not be determined by whether it resolves the dispute, but by whether it remains relevant to the process.