The Maoist Insurgency in Thailand was a 18-year long guerilla war (1965 - 1983) between Maoists (in the Communist Party of Thailand) and the government of Thailand, then backed by the USA, Taiwan and Malaysia (the Maoists were backed by China, Vietnam and North Korea).
Background
The insurgency was largely caused by anger at the presence of the US military in the country, inequality, repression of dissidents and the success of the Chinese Revolution. In the early 1950s, a group of 50 Thai communists traveled to Beijing where they receiving ideological and military training. In addition, the Pathet Lao set up small communist groups in 1961 and sent Thai communists to China, Laos and Vietnam to train. 350 Thai nationals trained and while they initially only had French, Chinese and Japanese weapons, they soon smuggled 3,000 US made weapons and 90,000 rounds of ammunition from Laos that the US sold to the Laotian army which they sold to smugglers and eventually the communists. From 1961 to 1965, the Maoists carried out 17 assassinations.
Events
In 1965, the Maoists began an all out guerilla war against the government, attacking police and military patrols. They also attempted to attack US military bases. In addition, after many Kuomingtang soldiers fled from China and became a part of the regions lucrative Opium trade the government repressed this and destroyed entire villages, providing a new population of recruits. The Maoists continued a small-scale guerilla war until 1983.
Repression
Content Warning: Extremely graphic descriptions of violence and torture
Main Article: White Terror (Thailand)
The government deployed massive counter-insurgency operations to crush the insurgents and assassinated their leaders and any sympathiers. Between 200 and 3000 Civilians who were suspected of supporting the government were placed in oil drums while half-conscious and burnt alive. Soldiers also raped and murdered university students suspected of supporting the insurgents.
Results
The insurgents declared an amnesty by 1980 and only small pockets of insurgents carried on the struggle, but by 1983 they have given up completely. Like most Maoist insurgencies, the one in Thailand was a complete failure.
References
https://en.wikipedia.org/wiki/Communist_insurgency_in_Thailand