A total of 104 customers, 99 of them Chinese nationals, tested positive for drugs during a police raid on buildings illegally operating as a nightclub in Bangkok’s Yannawa area on Wednesday.

Thirty-four luxury cars found in the buildings' grounds were impounded, including a Rolls Royce. The nightclub was said to be operated by a Chinese national.

More than 100 city police were involved in the raid on the Jinling, Leela and Wip Wup Car Wash buildings on Charoen Rat Road in Yannawa district around 3.30am.

They were acting on a tip-off the buildings were being used illegally as entertainment venues, with a karaoke bar to serve Chinese visitors, drug parties and illegal gambling, police said.

A total of 237 Chinese customers were detained, 111 men and 126 women. Twenty-nine others, mostly employees, were also held.

Police said all visitors and staff of the entertainment venues were made to take urine tests for drug use. A search of the karaoke rooms and other areas inside the buildings found at least 300 sachets of drugs such as ketamine and "happy water", a combination of several illicit drugs.

A police source said the nightspot had been operating for about four months. It mainly served Chinese customers. The Thais and Cambodians were employees there, and some worked for the Chinese customers. The owner was a Chinese national.