Assuming she works five days a week – and is booked up each night – Alicia is raking in about S$13,000 a month.

Ho says the sums prostitutes charge for sex services in Singapore vary widely, depending on where the woman plies her trade. “It can be as low as S$10 for a three-minute hand job, up to S$1,000 for a massage with sex,” she says.

Although Singapore does not stick too closely to the letter of the law, there are crackdowns. In May, 32-year-old Roderic Chen Hao Ren was sentenced to two years in jail and fined S$83,000 for operating a “virtual brothel” – a website advertising the sexual services of women at rates ranging from S$450 to S$600 an hour. He reportedly took 40 per cent of the women’s earnings.

Last year, Quek Choon Leong, 34, was jailed for 33 months for running a vice ring of 32 prostitutes, supported by his wife and 10 other staff.

In another indication of how the government is trying to keep a lid on illegal activity, the Ministry of Home Affairs said last month it had recorded a 40 per cent rise in the number of unlicensed massage parlours in Singapore between 2013 and 2016. These establishments, the ministry said, are often a front for vice activities.

Its findings prompted the introduction of a new Massage Establishment Bill to clamp down harder on operators, increasing fines tenfold to S$10,000, and introducing prison sentences of up to two years. The bill just has had its first reading.

In an attempt to regulate the sex trade, Singapore allows licensed brothels to operate in designated areas. The licensing process, controlled by the police, is murky and the number of establishments is not made public.

Ho describes the practice as part of the police’s “ring fencing” tactic for keeping prostitution in check. “Trying to eradicate vice is always a futile effort,” she says. “It is more important to allow zones for such activities.”

She estimates the number of licensed brothels at between 80 and 90, based on listings on the Sammy Boy website, where clients share prices and rate the women’s services.

The licensing of brothels is controversial because they operate in so-called designated red-light areas, where the law against pimping is not enforced, critics say. (These areas include the Geylang district, Keong Saik Road, Flanders Square and Desker Road.)

They argue that the brothels operate counter to the Women’s Charter, an act passed in Singapore in 1961 that prohibits knowingly living “wholly or in part on the earnings of the prostitution of another person”, and carries a prison sentence of up to five years and a fine not exceeding S$10,000.

“It is not just a grey area. It flies in the face of the rule of law,” Ho says.

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Dr Nicolas Lainez, who wrote a 2011 report for the Vietnam-based Alliance Anti-Trafic, wrote that the brothel owners’ profit is not considered a cut from sexual services but a charge for room rentals, among other costs.

“This subterfuge allows the brothel owners to circumvent the law that states that living on the earnings of prostitution is an offence as stipulated in the Women’s Charter,” he says.

Another place in Asia where prostitution is legal is Hong Kong, which also forbids soliciting, causing or helping another person to be a prostitute, and living off the earnings of a prostitute. However, there are no licensed brothels in Hong Kong, nor designated red-light areas. Wan Chai, on Hong Kong Island, has long been the unofficial red-light district, with bars and discos popular among Western clients, while Mong Kok in Kowloon is known more among locals for its illegal brothels and streetwalkers.

In 2016, Hong Kong accounting sector lawmaker Kenneth Leung Kai-cheong suggested the government establish a legal red-light district to consolidate and confine the sex industry. Secretary for Security John Lee Ka-chiu rejected the suggestion, saying prostitution in the city was already under control. He said setting up an official red light district would mean require big changes in government policy on the issue.

Unlike Singapore, Hong Kong does not outlaw classified ads for prostitution or websites that allow clients to make appointments. Sex workers get around the brothel rule by servicing clients in “one-woman brothels” that they can claim is their flat.

Despite the existence of licensed brothels in Singapore, many women still end up working illegally, including in an unknown number of unlicensed brothels. Some have even been found operating in public housing estates, The Straits Times reported last month.

There is clearly a demand for prostitutes in Singapore, Ho says, and women keep coming to the city from nearby countries such as Thailand, Vietnam, Indonesia and China.

Project X says there are many informal sex workers who work only occasionally, making it difficult to estimate the number. Two years ago, police arrested more than 5,000 unlicensed sex workers – mostly foreign women visiting on tourist visas.

Lainez says many are poorly educated with low-paying jobs back home. They came to Singapore for sex work to earn a higher income.

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Singaporean Jaafar falls into the same category. She failed to complete the Primary School Leaving Examination and has limited job options.

“Postnatal and body therapist, telemarketing, factory worker, cashier, stall assistant,” she says when asked about her previous jobs. She entered the sex trade 12 years ago when she needed to support her children after getting divorced.

“It is clearly not easy work, but they are caught in a very difficult place,” says Nicholas Harrigan, a sociologist from the Singapore Management University. “I would think the ethical thing to do is to look at how we can make their work safer and less precarious.”

They should be able to ply their trade safely, without harassment, and with dignity, Harrigan says.

After all, says Jaafar: “I am not just a prostitute. I’m actually a professional entertainer for the men in Singapore.”