"They told me 'if you confess, you'll just go to prison for four or five years," he said.
Zaw Lin and his fellow accused, Wei Phyo, who will also allege that he was the victim of torture, initially confessed to murdering David Miller and raping and killing Hannah Witheridge last September.
But they soon retracted the confessions, saying they were obtained by torture, and denied the murders.
A short distance away in the small courtroom in Koh Samui, Miller's parents, Ian and Sue, followed the testimony, grim-faced and heads bowed, as a translator whispered in their ears.
Also in court were the mothers of the two accused, who are both Burmese migrant workers. They could be sentenced to death if convicted. Zaw Lin's mother rushed out of the court and vomited during her son's testimony.
Wearing a brown prison tunic, the 22-year-old shuffled from the bench to the witness stand, bending down to hold the manacles that chain his feet each day for his court appearances.
His co-accused, Wei Phyo, 22, who is barely 5ft tall and also manacled as he watches proceedings, will testify at a later hearing.
The two men both worked in the tourist restaurants and bars along Sairee Beach, an arc of palm-tree lined sand that attracts young visitors such as Miller, who was 24, and Witheridge, 23.
After finishing work one evening last September, Zaw Lin described how he went drinking with his fellow defendant and another Burmese friend on the same beach where the bodies of two British victims were found at dawn the next day.
Prosecutors have alleged that the accused men killed Miller and then raped and murdered Witheridge after they saw the Britons having sex on the beach.
The victims were not a couple and no evidence has been presented that they were having sex when attacked.
For Miller's parents, on the island this week, and for Witheridge's family, who have followed proceedings from Britain via reports supplied from court, the proceedings are about justice for their murdered children.
"Please remember that this is above all a story of two wonderful young people, David and Hannah, killed in the prime of their lives in a senseless and brutal way," said the Miller family in a statement.
But in many ways, it is not just the two young Burmese men who have been on trial since the case opened in July.
So is the Thai justice system as the men's supporters argue that they were tortured and framed at a time when the county's new military rulers were desperate to declare the case solved and reassure tourists that Thailand was safe.
In key testimony, prosecution witnesses have told the court that DNA recovered from Witheridge's body matches that of the two accused.
But the defence has disputed the accuracy of the forensic analysis, which was conducted by the Thai police and not an independent body.
- Daily Telegraph