A Thai police probe into a gang that  allegedly procured teenage sex slaves has ensnared at least four officers,  investigators said Monday, the latest scandal to engulf a force with an already  poor reputation.

Revelations of a child sex ring first emerged last week when a mother said  her teen daughter had been pimped out for the last year to influential  officials in northern Mae Hong Song province, one of Thailand's poorest regions.

Days of lurid headlines followed with allegations that senior police and  regional officials were involved in the ring.

On Monday national investigators confirmed warrants had now been issued for  four officers with the rank of sergeant and above.

"A court today issued arrest warrants against three policemen for raping  women," deputy national police chief Srivara Ransibrahmanakul said.

A warrant has also been issued for a fourth officer and two female pimps have already been arrested.

At least eight other people -- including three high ranking police officers -- are under investigation as suspected pimps, he added.

Thailand's police forces have a notorious reputation for corruption, a scourge that can be even more acute in the regional provinces.

Prostitution is illegal yet ubiquitous in the kingdom and rights groups  have long accused police of pocketing bribes to turn the other cheek or taking  active part in the trade.

A raid on a large brothel in Bangkok last year uncovered a "tea-money"  (bribery) log book detailing payments to local cops.

Yet police are rarely sacked or imprisoned for such transgressions.

But the Mae Hong Song sex ring has hit a nerve.

The lawyer for the girl's mother told AFP she had been trying for months to  get police to investigate with little success until she went public.

"There were times when she was asked to compromise the case by some police  officials", Kerdphol Kaewkerd said.

The mother worked as an informant for the authorities and discovered through police contacts that her daughter was being pimped out.

She ended up contacting her daughter through a Line group used to advertise  the girls by pretending to be a client.

"The daughter herself showed up," Kerdphol said.

Rights groups have long urged Thailand to do more to crackdown on traffickers and pimps while decriminalising sex work to make it safer for those  selling their bodies.

But there has been little public policy debate by successive governments in  a country that remains conservative despite its party reputation overseas. (AFP)