A rice farmer from Svay Rieng province yesterday told the Khmer Rouge tribunal of his time as a Khmer Rouge spy who fled a vicious purge, ultimately defecting to the Vietnamese forces he was once tasked with monitoring.

Chhun Samorn, now in his late 50s, joined the Khmer Rouge as a messenger, and in 1976 was transferred to a special unit within the East Zone to gather intelligence on Vietnamese troops at the border.

“Wherever there were Vietnamese soldiers, I went there to collect intelligence information . . . about their bases, about their weaknesses and strengths, so we could plan our attack,” Samorn said.

But in 1978, after intense clashes at the border, Khmer Rouge soldiers from the capital and the Southwest Zone arrived and told troops in the Eastern Zone to lay down their guns and reveal where land mines were planted, before telling them they would be sent to Phnom Penh and re-armed.

Instead, the soldiers were loaded onto a truck and taken to a site at a farm rice, where they saw a fellow Eastern Zone cadre who had disappeared. “Then we knew that this was a lie.”

A group of 29, including Samorn, were tied up and “herded like animals” to an execution site.

He “was the only one who dared to protest”, and was struck with the butt of a rifle, partially paralysing his right arm. Four of his comrades were then separated and shot.

“We heard the screams, so we panicked and tried to escape,” Samorn said. “Those who could not escape were shot dead with their hands still tied up . . . Only three of us managed to escape and survive the ordeal.”

Samorn said he untied his hands and fled with two comrades, but three soldiers were in pursuit. The escapees jumped into a river and managed to dodge the soldiers’ fire before “running the whole night” to cross the Vietnamese border, where they were shot at again by the Khmer Rouge.

Far from “disembowelling prisoners”, as the Khmer Rouge had led Samorn to believe, the Vietnamese saved the escapees by firing back, bandaging their wounds and encouraging them to join the invasion force they were prepping to overthrow the Khmer Rouge.

While the Khmer Rouge had accused him of being a traitor, Samorn insisted yesterday he had “had confidence in the Khmer Rouge revolutionary army because I thought they were faithful to the Cambodian people”.