A three-day islandwide police operation which ended on Friday saw 38 people arrested - including an 80-year-old - for vice, gambling and immigration-related offences.
One woman was arrested for using criminal force against a public servant.
In total, 19 women and 19 men, aged between 21 and 80 years old, were nabbed during the operation which was conducted in areas such as Jalan Besar, Beach Road, Telok Blangah Rise and Bendemeer Road.
On Friday, The Sunday Times accompanied plain-clothes officers from Central Police Division as they raided a crowded coffee shop in French Road, near Jalan Besar Stadium, at 7.45pm.
The officers found several men holding slips of paper in which they wrote down their bets.
The suspects were lined up - some protesting loudly - before being handcuffed, led to a police vehicle and taken away around 8.20pm.
At around 10.30pm, plain-clothes officers arrested two women at a coffee shop in Syed Alwi Road and another two at a coffee shop in Verdun Road in Farrer Park.
The Sunday Times understands that the women are Indian nationals who are in Singapore on special passes, and were allegedly soliciting at the coffee shops. They are believed to be part of a syndicate.
In all, 11 women were picked up for offences under the Women's Charter.
In a statement, police said they are believed to have been operating from hotels and rented apartments while residing in Singapore on Employment Passes and Short Term Visit Passes, making use of their stays here to provide paid sexual services.
Fifteen men and seven women were arrested for gambling-related offences and offences under the Remote Gambling Act. About $2,400 in cash was seized.
The remaining four men were arrested for immigration-related offences.
In the statement, police said they will "spare no effort and continue to clamp down on vice and criminal activities". "Those found engaging in illicit activities will be dealt with sternly in accordance with the law."