Massacre of students gathering at Thammasat University in Bangkok, Thailand, to protest the return of ex-dictator Thanom, by a coalition of right-wing paramilitary and government forces, triggering the return of the military to government.

The 6 October 1976 massacre, or the 6 October event (Thai: เหตุการณ์ 6 ตุลา RTGS: het kan hok tula) as it is known in Thailand, was a violent crackdown by Thai police and lynching by right-wing paramilitaries and bystanders against leftist protesters who had occupied Bangkok's Thammasat University and the adjacent Sanam Luang, on 6 October 1976. Prior to the massacre, thousands of leftists – students, workers and others had been holding ongoing demonstrations against the return of former dictator Thanom Kittikachorn to Thailand since mid-September. Official reports state that 46 were killed (both sides) and 167 were wounded, while unofficial reports state that more than 100 demonstrators were killed. In the "Documentation of Oct 6" project, Thongchai Winichakul argued that official death toll should be 45, 40 demonstrators, 5 perpetrators because one demonstrator died in jail after the incident.In the aftermath of the events of 14 October 1973, the military dictatorship which had ruled Thailand for more than a decade was overthrown. Political, economic and ideological factors caused the society to polarize into socialist-minded left, and conservative and royalist right camps. The unstable political climate which was exacerbated by the existence of fragile coalition governments, frequent strikes and protests, and the rise of communist governments in neighboring countries led at least two factions of the armed forces to conclude that they needed to launch another coup in order to restore order; one faction plotted to bring Thanom back in order to provoke turmoil which could be used to justify a coup. On 19 September 1976, Thanom returned to Thailand, was instantly ordained at Wat Bowonniwet Vihara, and was visited by the King and the Queen, resulting in anti-Thanom protests and demonstrations. On 5 October, the protesters were accused of lese-majeste following a mock play which led to right-wing allegations that its actor looked like the Crown Prince; the police and rightist paramilitary groups then gathered outside the university.

At 5.30–11.00 a.m. on the morning of 6 October, the police used war-grade weapons, including assault rifles, grenade launchers, anti-armor rounds and grenades, to wage the crackdown against the surrounded protesters. The protesters briefly tried to defend themselves, but they were quickly defeated. Right-wing paramilitaries also lynched fleeing protesters; they were assaulted, robbed, sexually abused, shot, burned alive, and beaten to death, even some who had already surrendered. Bodies were also desecrated. 3,094 protesters were arrested on that day, while none of the perpetrators were brought to justice to date. On 6.00 p.m. that same evening, a coup was launched citing lèse-majesté and heavily-armed protesters.

In the aftermath, the preceding age of "democratic experimentation," which had lasted only about two years and eleven months, was ended. Thanin Kraivichien was named Prime Minister and the ultra-right government further fuelled the communist insurgency. The public were largely silent following the government stance of "forgive and forget", including the modern Thai public who are more sympathetic to the massacred protesters. Scholars have pointed out that the monarchy contributed to the events, at least partly, by supporting the rightist paramilitaries and the visit of Thanom.: 31