It is as if you have walked into a branch of one of Vietnam’s banks. A row of customer service desks, divided by plastic screens, with landline phones, promotional leaflets and staff business cards. A seated waiting area and a private meeting room. All of it features the OCB bank’s logo, or its trademark green colour.

This is not a genuine bank branch, however. It’s one of various “mock up” rooms inside a sprawling compound on the Thai-Cambodian border, where criminal groups are accused of using elaborate and industrial-scale fraud schemes to trick victims into handing over money.

The scammers behind the compound targeted people not just in Vietnam, but across Asia, Australia and South America, according to documents and props discovered inside.

Within the six-floor building, in the Cambodian border town of O’Smach, there are rooms designed to look like offices for police forces from Australia, Singapore and China. There are even fake uniforms, badges and scripts to be read over the phone to victims.