BY day, the forested area appears abandoned and empty. But when darkness falls, mattresses and cardboard sheets are laid on the ground - ready for business.

Instantly, the area is transformed into a makeshift love camp - a hotbed of sex, gambling and other illegal activities.

The issue of forest brothels, where foreign workers go for cheap sex, caught international attention when the Bangkok Post reported last Sunday that Thai women were trafficked every year to remote locations in Singapore where they were held as 'sex slaves'.

A Thai academic here backs up the report, adding that such vice parties are still happening almost every weekend in various parts of the island.

Dr Pattana Kitiarsa, a Thai anthropologist with the National University of Singapore's Southeast Asian Studies Programme, told The New Paper on Sunday: 'It is a difficult issue to deal with because of the sheer volume of foreign workers in Singapore.

'There are more than 600,000 men here who are either single or away from their wives and girlfriends. Where there is demand, there will be supply. It is almost impossible for the police to be conducting raids every week at various parts of the island.

'So while Singapore authorities are strict about the problem, it is hard to prevent such activities from happening every weekend.'

In July this year, police busted a vice den for foreign workers at Loyang Way and arrested five men and a Thai prostitute. The barren field near Pasir Ris had been a haven for gamblers and foreign workers seeking cheap sex.

In March, the police found another forest brothel in Yishun operated by Thai nationals.

Previously, they had also raided wooded areas in Lim Chu Kang Road and Woodlands.

The existence of such vice dens first came to light after the murder of a Thai man in 2001 by two other Thai men in a forest hideout off Boon Lay Way.

The group had been fighting over an illegal Thai immigrant - a prostitute who also helped sell drugs.

The police raided the site and flushed out 245 people, including 23 women, all of whom were Thais.

Said Dr Pattana, who teaches English to Thai workers on Sundays at the Golden Mile Complex: 'I've personally witnessed such activities in four to five different locations in Singapore last year and this year.

'Although Singapore is one of the strictest countries I know regarding the issue, it's a problem that keeps popping up.'

The Bangkok Post reported that many of the women working in such forest brothels are held in debt bondage to the agents who brought them to Singapore.

The article estimated that several hundred women worked in Singapore's forest brothels at any one time.

The Bangkok Post reported that those interviewed speculated that policing of such brothels is 'rare because they're silent, out-of-sight operations that don't cause trouble for Singapore or its citizens'.

The article also stated that such operations exist largely because of Singapore's 'blind-eye approach to trafficking and the strict sexual code that governs its migrant workers'.

But lawyer and ex-police officer A P Thirumurthy felt the report wasn't fair.

He said: 'Vice is a problem no country can eradicate fully, but as soon as our authorities learn of such forest dens, they act on it and flush the involved persons out.

'The article is based on anecdotes and speculation. If there are no hard figures on the number of activities going on, it's hard to believe that the problem is rampant here.'

Those who work with foreign workers here say the problem is not as severe as the article made it out to be.

Ms Bridget Lew, founder and president of the Humanitarian Organisation for Migration Economics (Home), which runs a shelter to help foreign workers, said she saw five such cases four years ago - involving two Thais and three Vietnamese women.

She has not seen similar cases since.

This article was first published in The New Paper on October 19, 2008.