Police raided an underage brothel disguised as a karaoke bar in Thailand.

Police descended on the Pak Thang Phrao music bar after receiving reports that it was unlicensed and operating past hours in Chiang Rai province on November 13.

An undercover agent visited the establishment and confirmed that it was still open past midnight.

Officers then barged inside and reportedly found underage girls as young as 13 drinking alcohol with the customers and belting out tunes on the karaoke.

Police said there was a common area and a VIP room where female staff 'provided services' for patrons. Twelve methamphetamine pills were also found on the premises.

The raid was expanded to a nearby hotel where customers allegedly bed the young bar girls. Two underage hookers were rescued.

Acting provincial governor Chotinarin Kerdsom, who oversaw the raid, said: 'We arrested an individual who claimed to be the manager but could not produce a license for the bar.'

The suspect was charged with operating an entertainment venue without permission, selling alcohol beyond legal hours, inducing or encouraging minors to behave inappropriately, and employing minors.

Authorities said the teenage staff will be interviewed to gather evidence and determine if they were victims of human trafficking.

Underage prostitution is fairly common in Thailand despite government efforts to curb it through strict laws and enforcement initiatives. Driven by poverty, trafficking, and lack of education, vulnerable minors are sometimes forced into the sex industry to earn money.