Youk Chhang remembers the first document he uncovered; it’s still sitting on his desk. Under a staircase in an old government building in the early 1980s, Chhang found a booklet spilling with testimonials, locations of mass graves and inked thumbprints details of the atrocities millions of Cambodians suffered under the Khmer Rouge regime.

The booklet was intended to go to the UN but never left the country, according to Chhang. Instead, it became the cornerstone of what is now the Documentation Center of Cambodia (DC-Cam), which boasts thousands upon thousands of documents and photographs.

Chhang, the centre’s director, is due to receive a prestigious human rights award in San Francisco today in recognition of his efforts to chronicle the Kingdom’s dark past.

Chhang was chosen for the Center For Justice and Accountability’s Judith Lee Stronach Human Rights Award because he “has dedicated himself to collecting evidence of crimes against humanity committed by the regime, and has been instrumental in the prosecutions of senior Khmer Rouge officials”, the organisation wrote in a statement.

“Documentation is a political act,” Chhang said in an interview with The Post earlier this week. “It’s not a piece of paper you put in a cupboard. When you take a piece of paper, you have to ask yourself why, and for whom? It is required in transitional justice, for atrocities or conflicts or genocide.”

When the colossal task of documenting the crimes began, some 22 years ago, Chhang faced obstacles. While the then-Vietnamese-backed government supported amassing evidence, the Khmer Rouge – still active in the northern reaches of the nation – threatened his life.

“I got death threats every week from the Khmer Rouge at that time . . . [They] sent a couple of their soldiers to my sister’s house, to tell me to stop. It was Ieng Sary,” Chhang said, referring to one of the communist movement’s most senior leaders.

Chhang chose not to run to an embassy for help. Instead, he said, he went to Sary’s door, knocked, and simply asked to see his wife, Ieng Thirith, also a senior figure in the Khmer Rouge. It was a kind of “threat” in return, Chhang said, to show he would not be cowed.

Under the Khmer Rouge, Chhang was forced into work as a 14-year-old boy and was tortured for picking mushrooms for his starving, and pregnant, sister. He prefers not to count the number of family members lost; only a handful survived. He never saw his uncle die, and so his mother continues to believe he is living, somewhere.

“Sometimes the imagination helps,” he said. He recalled receiving a book from a young man; it was penned by the man’s mother and was a fictional story of two brothers divided by the regime.

“He told me part of the book is not true . . . but any story that people can share can help bring closure to the entire nation, even if it’s a fiction.”

Chhang said the centre receives photographs and documents from around the country every week, and encourages those who suffered to tell their children, any way they can.

In receiving the award, Chhang joins other human rights luminaries. Previous recipients include the former UN High Commissioner for Human Rights Navi Pillay; Guatemala’s first woman attorney-general, Claudia Paz y Paz, who tackled organised crime; and forensic anthropologist Jose Pablo Baraybar, who conducted investigations to prove genocide had occurred in Srebrenica, Bosnia and Herzegovina.

“To me, it’s testimony that no one can eliminate humanity completely, and that even though sadly it took such tragedy to come this far, I am pleased we are making sense out of it at DC Cam. That’s something I’m very proud of,” Chhang said.