Thai Resort Island at the Center of a Simmering Territorial Dispute With Cambodia

An idyllic island in the Gulf of Thailand has recently become a subject of contention between nationalists in Thailand and Cambodia, derailing negotiations over the joint exploitation of offshore gas reserves.

Koh Kood is a popular holiday hotspot for foreign tourists to Thailand, attracting hundreds of thousands of visitors each year. But Cambodian activists and nationalists have recently reignited a decades-old territorial dispute, claiming that the island partly belongs to Cambodia.

Hun Manet, the prime minister of Cambodia, recently waded into the debate, publicly stating that its claims over Koh Kood, which is referred to as Koh Kuch in Khmer, had not yet been lost.

The disagreement over Koh Kood dates back to the era of French colonial rule in Indochina. In 1904, Thailand, then called Siam, ceded the island to France, along with the nearby port of Trat and other adjacent islands. In the Franco-Siamese Treaty of 1907, these territories were then retroceded to Siam in exchange for large territories in western Cambodia.

However, Cambodia has never fully accepted Thai sovereignty over Koh Kood. In 1972, Phnom Penh released an official map and normalized its continental shelf with a decree that asserted a claim over the southern part of Koh Kood.

Koh Kood is internationally recognized as part of Thailand, and the Thai government claims the island on the basis of the 1907 treaty, as well as under international maritime law.

The fourth-largest island in Thailand, Koh Kood is located in Trat province in the Gulf of Thailand, near the maritime border with Cambodia. Although claims over its ownership linger, Koh Kood’s laid-back atmosphere – marked by soothing beaches, luxury resorts, and turquoise waters – masks any signs of tension on the island.

But despite the island’s placid nature, Cambodian claims to the island are getting louder.

Over the past two years, diaspora groups around the world have held protests over Koh Kood, with recent demonstrations in Australia, Canada, France, South Korea, Switzerland, and the United States.

Mu Sochua, a Cambodian politician and president of the U.S.-based Khmer Movement for Democracy, said that Cambodian diaspora communities are demanding that the Koh Kood dispute be heard by the International Court of Justice (ICJ) in The Hague, Netherlands.

“Based on official documents, part of the island belongs to Cambodia,” Mu Sochua told The Diplomat, referring to the 1907 treaty.

Sochua said that her group would present its recommendations for Koh Kood to Cambodian King Norodom Sihamoni and the Cambodian government via the Cambodian Embassy in Washington, D.C., on May 10. It hopes that the government will bring the case to the ICJ.

However, Tita Sanglee, a Diplomat columnist and associate fellow at Singapore’s ISEAS-Yusof Ishak Institute, said that Cambodia’s claims over Koh Kood are contentious.

“Cambodia’s claim was rooted in a different interpretation of the said treaty,” she said. “It should be noted that the 1907 Treaty, like other treaties of its time, intended to address land, not maritime, boundaries. This is why the Cambodian interpretation is controversial.”

Offshore Bounty

The dispute over Koh Kood resurfaced in 2024 when misleading posts on the social media app TikTok showed Thailand transporting military vehicles for exercises close to the island. The video turned out to be fake, as did other rumors claiming Thai and Cambodian military forces had been involved in a skirmish near Koh Kood.

This happened even as Thailand and Cambodia announced their intentions to reopen negotiations over their maritime border in the Gulf of Thailand, which has remained undemarcated since the Franco-Siamese Treaty of 1907. The disputed area, known as the Overlapping Claims Area (OCA), totals around 27,000 square kilometers and is believed to contain underwater resources, including significant natural gas reserves.

In 2001, the two sides signed a Memorandum of Understanding to act as a framework for negotiations over the OCA. Then-Prime Minister Thaksin Shinawatra urged both Thailand and Cambodia to resolve the dispute so that they could benefit economically from the potential energy resources in the Gulf, but negotiations petered out after Thaksin’s removal in a military coup in 2006.