A tuition agency owner who hired women online to sell sexual services was jailed 15 months and fined $12,000 after admitting guilt.

Singaporean Desmo Vu, 32, faced 17 prostitution-related charges for which prosecutors proceeded with four counts of living off the women's earnings and two counts of recruiting the women to sell sex.

Vu, who set up a website in 2014 to lure the women exercised "substantial control", which included requiring them to declare the specific sex acts they were prepared to perform.

The women, five of whom were witnesses aged between 24 and 32 years old, had to sign written contracts which set the booking terms, such as the minimum duration for each booking, the sums payable and his share of the takings.

The women included Malaysians as well as Indonesian and Taiwanese permanent residents here, who were variously occupied as hairstylist, data processor and students.

Vu had nine women working under him who averaged nine clients each over a 10-month period from December 2014, based on the charges that were proceeded with. This netted him some $10,960.

He had placed a minimum booking of two hours for his social escorts at a booking fee of between $800 and $1,600 that he would set after assessing their individual personalities and looks.

Deputy Public Prosecutor James Chew urged the court to have three jail terms run consecutively, pointing to the aggravating features of the case.

Among other things, he pointed out that this was a sophisticated enterprise masterminded by Vu, who went online to ensure a "wide clientele reach".

Defence lawyer Patrick Chin countered that Vu had tried to run a legitimate social escort agency dwelling on companionship, and anything else was worked out between the clients and the women themselves.

District judge Lim Keng Yeow was not convinced, noting, among other things, that Vu had "made it a point to tell the females to bring their own condoms" since it was common knowledge the clients expected sex.

"In addition... it seemed obvious that the booking fee fixed by Vu already contemplated the provision of sexual services," added the judge in the judgment grounds released yesterday.

The judge said the "exorbitant fees" charged also inferred that sexual services would be provided without further negotiations.

"These facts clearly did not show that Vu held a naive view as to what the engagement of the females had to do with."

Judge Lim said the sheer number of charges and the duration of the offences justified imposing three consecutive sentences instead of the usual two sentences with the others to run concurrently.

The judge added the $12,000 fine in the light of his "earnings from his offences".