Surapong says he worked as a male prostitute until he contracted a sexually transmitted disease.

Surapong Trakulrak was arrested at the Big C Supercen-tre at Ramkhamhaeng on Wednesday night after the father of his latest victim, a 13-year-old boy who had been missing since Sunday, received a phone call on Tuesday demanding a Bt50,000 ransom and alerted the police.

Surapong was charged with luring a minor and extortion and presented at a police press conference yesterday.

Surapong told reporters he was a Mathayom 3 graduate who came to Bangkok to find a job but ended up as a homeless person. He said he was a homosexual and worked as a male prostitute until he contracted a sexually-transmitted disease.

He said he started his kidnapping and extortion spree in 2004 after overhearing a group of students at a shopping mall warning each other about student inspectors - students who volunteer to inform on any inappropriate behaviour by them, such as truancy.

Surapong admitted molesting some of his victims and forcing them to perform oral sex on him in exchange for letting them go.

Metropolitan Police chief Lt-General Adisorn Nonsee said Surapong had confessed to kidnapping about 200 students before he was finally arrested on Wednesday.

"The suspect's actions are a threat to society and he must face serious punishment," he said.

Adisorn said parents and youths should be aware of the danger of people posing as student inspectors to extort money or sexual favours from students.

He said police would investigate whether Surapong had accomplices and urged parents of children he had kidnapped to file complaints at Lat Phrao police station.