Seven friends decided to demand "protection money" from a massage parlour offering sexual services, as they believed the owner would not call the police, a court heard.
But they were mistaken and one of them, 27-year-old Douglas Cher Ze En, was yesterday jailed for 10 weeks and fined $30,800.
He pleaded guilty to four charges: criminal intimidation, behaving in a disorderly manner, assisting an unlicensed moneylender and having an offensive weapon. Four other similar counts were considered in sentencing.
A district court heard that Cher's friend Wu Wai Chung, 25, hatched the plan to extort money from a spa which offered sexual services, and then told his friends about the scheme on Nov 23, 2014.
At about 10.30pm that day, one of them, Alex Lai Shizheng, 24, "obtained massage services and confirmed that the spa did indeed offer sexual services", the court heard.
Lai then contacted the rest of the group, most of whom went to the spa. The next day, Wu again got a massage at the spa. After the session ended just after midnight, the rest of the group met him there.
Wu then told a 44-year-old receptionist that he would refer customers to the spa if given a commission - but she declined the offer.
The seven friends then shouted at her and Wu kicked a glass cabinet, damaging it. Wu told the receptionist it was merely a warning and that he would return the next day to collect $5,000. If he was not paid, he warned, the group would cause further damage. The receptionist called police after they left the spa.
Two in the group have been sentenced to probation. Wu is believed to be at large. Lai got a conditional stern warning for his role. The case for one man is before the courts, while another faces separate charges for another case.
The charge of behaving in a disorderly manner stems from a pub brawl on Nov 22 that year when Cher kicked and punched an unknown patron and punched another man's face at about 1.35am at the JD Pub in Golden Mile Complex.
Cher later took out a Swiss Army knife "with the intention of striking out at anyone who dared to come near him," the court heard.
On Nov 20, Cher was found with a truncheon at a cinema in Yishun.