Cambodia launches UNCLOS Annex V 'compulsory conciliation' against Thailand over 26,000 sq km, $300bn Gulf of Thailand gas zone after Bangkok quits 2001 MOU

On June 2, 2026, Cambodian Prime Minister Hun Manet announced Cambodia would invoke 'compulsory conciliation' against Thailand under Annex V of the UN Convention on the Law of the Sea (UNCLOS) to resolve the long-frozen Overlapping Claims Area (OCA) in the Gulf of Thailand. The disputed zone spans roughly 26,000 sq km and is estimated to hold oil and gas reserves worth about US$300 billion (over THB 10 trillion). The filing directly answers Thailand's unilateral withdrawal, the prior month (May 2026), from the 2001 Memorandum of Understanding (MOU-2001) that had governed boundary talks.

Hun Manet framed it as lawful: 'This is not unilateral action. It is an effort to resolve the dispute peacefully, through international law, and in good faith.' Cambodia named Foreign Minister Prak Sokhonn as principal representative and appointed Danish diplomat Peter Taksoe-Jensen and French academic Jean-Marc Thouvenin as its conciliators; Thailand has 21 days to appoint its own before a commission chair is selected. A conciliation committee then has 12 months to issue a non-binding report.

Thai Foreign Minister Sihasak Phuangketkeow rejected the move, saying it undermined trust and complicated a negotiated settlement, insisting talks should follow UNCLOS bilaterally — consistent with Bangkok's historic aversion to third-party adjudication (it has long rejected the ICJ's Preah Vihear ruling). The dispute follows 2025 border clashes that killed roughly 150 and displaced about 500,000, and a December 2025 ceasefire.