In four years, he made more than a million dollars from his nine pubs in two Orchard Road buildings.
But about 40 per cent of that money was made illegally by providing sexual services in the pubs.
His customers had to buy a certain number of "ladies drinks" at inflated prices to qualify for such services as oral sex inside the joints.
They could also pay a "bar fine" of at least $200 to take a woman out for activities that usually included sexual intercourse.
To provide these sexual services, pub owner Ang Boon Seng and his 18 accomplices, including his wife, procured women from the Philippines.
Ang, 40, is awaiting sentencing for abetting with others to procure women for the purpose of prostitution, abetting with others to harbour the women, living off their immoral earnings and managing brothels.
He faced 232 charges in total, with 189 taken into consideration and six earlier discharged amounting to acquittal.
His wife, Ylarde Anne Asuncion, a 31-year-old Singapore permanent resident from the Philippines, is also awaiting sentencing for six charges of procuring women for the purpose of prostitution and one count of living off immoral earnings.
They pleaded guilty in August.
Court documents revealed that Ang opened his first pub, Tokyo Drift, in Orchard Plaza in June 2009.
Based on his efforts and experience in the industry, the business prospered and by August 2013, he had opened another eight.
Six of them, including Poker Face Entertainment, Masquerade Karaoke & Tea Lounge and Koto Japanese Lounge, were also in Orchard Plaza, with the remaining two, Ginza Entertainment and Candles Pub, in nearby Cuppage Plaza.
A check by The New Paper last night found that most, if not all, of the pubs have closed down.
Ang employed a total of 55 women who worked as "performing artists" in his pubs. Ten of them, aged between 21 to 29, were involved in the charges proceeded against him.
Before coming to Singapore, the women were told they were bound to a "utang" (which means "debt" in Tagalog) - a verbal contact that needed to be fulfilled before they got paid. In one case, the woman's "utang" was $5,600.
To offset the "utang", the women had to provide sexual services.
They could do so by earning points through selling "ladies drinks" - each costing $22 to $55. Each point was worth $4.
The women were also told that they could offer sexual services after the customers had purchased a minimum number of these drinks, which could amount to a few hundred dollars.