The Kingdom of Siam exercised a loose sovereignty over the northern part of the Malay Peninsula, including the Malay Sultanates of Kedah, Kelantan, Pattani, Perlis and Terengganu, from the 16th century (see History of Thailand). In 1902, Pattani was formally annexed by Siam. Seven years later, under the Anglo-Siamese Treaty of 1909, the British colonial administration in Malaya forced the King of Siam to cede sovereignty over all of these except Pattani to Britain, while the British recognized Siamese sovereignty over Pattani, which became a monthon (region) of Siam. In 1933 the monthon was divided into the provinces of Narathiwat, Pattani and Yala.
During the 20th century the area was, to some extent, assimilated into Thai society. Most people acquired Thai names, and there was substantial Thai Buddhist settlement in the area. Today Thai is the language of the government and of business; most southerners speak and understand Thai. But some 2.6 million people in the three provinces, as well as some districts in Songkhla province, still speak Malay as their first language, and have remained Muslims despite considerable Buddhist missionary efforts.
Over 80% of the population in Pattani, Yala and Narathiwat continue to adhere to Islam. However, the Pattani Malays have little sense of connection with the Malays of modern Malaysia, and they speak a distinct local version of the language known as Yawi.
There has been a separatist movement in Pattani since at least the 1930s, but under successive Thai military regimes it was firmly suppressed. During World War II, when Thailand under the nationalist regime of Marshal Plaek Pibulsonggram was an ally of Japan, Tengku Mahmud Mahyuddin, a prominent Pattani leader who was the son of the last Raja of Pattani, allied himself with the British in promises that after the war should they win, Pattani would be granted independence. After the war, there was an attempt to establish a "Greater Malay Pattani State" (Negara Melayu Patani Raya), but the British gave this movement no support and hopes of an independent Pattani were shattered.
In the late 1940s when the Pibulsonggram regime tried to impose Thai-language education on the area the Pattani leader Haji Sulong Tokmina (who had supported the Japanese during war as a rival to the pro-British Tengku Mahmud Mahyuddin), wanted cultural autonomy but not independence. He was imprisoned in 1948 and killed by police shortly after his release in 1952. There was then little overt secessionist agitation until the liberalization of Thai politics in the 1980s, but separatist groups such as the National Revolutionary Front (Barasan Revolusi Nasional, BRN) survived and maintained a base of support.
Renewed agitation began in the 1990s, led by Malay intellectuals influenced by revolutionary and Islamist ideas from the Middle East. The BRN split into three rival factions, of which the most militant were the BRN Coordinate and the BRN Congress. The BRN Congress is now regarded as the most active group, but there are several others, and competition between these militant groups has helped fuel the insurgency. It is believed that there is now a co-ordinating body called the Pattani United Liberation Organization (Dewan Pembabasan Pattani or PULO), although little is known about the composition or leadership of the various groups.
PULO's platform is highlighted by its Islamic nationalist goals, calling the Thai presence in Pattani "a colonisation" and an "illegal occupation." Its stated aims are to secede from Thailand through military and political means, and to create a state named Patani Darul Makrif (Pattani, Land of Good deeds). The PULO flag has four red and white stripes and a blue rectangular on the upper left with a crescent and a star similar to other Malaysian Malay states