The killings of Oct 6, 1976 marked a nadir in the nation’s recent bloody political history.
At least 46 student students were shot, beaten to death or hanged from trees after they massed at Thammasat University in protest at the return from forced exile of hated military dictator Field Marshal Thanom Kittikachorn.
Survivors say the true death toll was at least twice as high, with thousands more arrested or forced into hiding.
Fearing a leftist rebellion in a region where many countries had become communist, security forces – flanked by armed militias – ruthlessly cracked down on the students.
No state apology has ever been issued and no officials have been held to account for the deaths – a reflection, critics say, of a culture of impunity for the military that endures to this day.
At dawn on Thursday survivors gathered under heavy drizzle around a permanent memorial at the university’s entrance, where the assault began.
Some held candles, others wore T-shirts with the slogan “I think therefore I am dead” featuring a hanged man – a reference to the lynching of students who were strung from trees near the campus.
“There were many killed and injured on that day,” said Sinsawat Yodbangtoey, 63, who was an art student at a nearby college when he joined the Thammasat protests.
“Even though I wasn’t injured… my heart is wounded.”
The Oct 6 crackdown ended a brief three-year flirtation with democracy and ushered in another 16 years of military-led rule.
Thailand is once again under military rule, with the country’s democracy movement hemmed in by repressive laws.
The last coup in 2014 – the army’s 12 successful power grab since 1932 – came four years after soldiers once more opened fire on pro-democracy protesters on Bangkok’s streets during the red-shirt protests of 2010 against the Abhisit government.
Many newspapers nonetheless used the rare space provided by Thursday’s anniversary to recall dark chapters from the military’s past, while graphic photos of student hangings were widely shared on Thai social media.
Sirawith Seritiwat, a 24-year-old Thammasat student and one of a handful of activists protesting against the current junta, said remembering the past is vital in a country with a proclivity for collective amnesia over difficult events.
“There was an effort by many people, (Thai) governments and leaders, to forget history,” he told AFP.
“They want reality to be hidden.”
Former politician and student leader Prommin Lertsuridej, 62, who fled to the jungle for four years to avoid arrest after the protest, said October 6 was a “hugely important” moment in modern Thai history.
“We gather every year to show we were not the people who destroy the country – we are the ones who want to create a fair society,” he added.