Malaysia–Thailand border

Siam and the sultanates

Between 1824 and 1851 Bangkok drew the Malay sultanates of Trengganu, Kedah, Kelantan and Pattani closer, while Britain spread its protection over the states to the south. The two met, and a first boundary treaty on Kedah’s frontier followed in 1869. In the treaty of 1909 Siam gave up its claims over Kedah, Trengganu, Perlis and Kelantan to Britain, and that treaty set the present border. Thailand briefly regained the four states in the Second World War, and in 1957 they became part of independent Malaya.^[1]

From the mangrove coast of the Strait of Malacca the line follows watersheds over the Sayun Range and the forested granite Central Highlands, then the meandering Golok River across the eastern plain to the Gulf of Thailand.^[1]

“Commencing from the most seaward point of the northern bank of the estuary of the Perlis River”^[1]

The Deep South

Pattani, Yala and Narathiwat, just north of the border, belonged to an independent Malay Muslim sultanate before Thailand annexed them in 1909, and their population is about 80 percent Muslim. More than 7,000 people have died there since 2004 in drive-by shootings and bombings by separatists; Malay Muslims accuse the security forces of arbitrary detentions and extrajudicial killings.^[2]

Malaysia has hosted and facilitated talks between the separatists and the Thai government since 2013. In February 2024 both sides agreed in principle on an improved peace roadmap in Kuala Lumpur.^[2]