In January, 23-year-old Mah (not his real name) boarded a flight that would land him a lucrative job at a casino in Sihanoukville, Cambodia. Or so he thought.

The Sibu native was told about the job by a friend and so he took the plane from Singapore to Phnom Penh before travelling down to Sihanoukville, a port city in Cambodia’s southwest.

Instead of a well-paid casino job, Mah found himself ensnared by...