A 17-year-old, who found out that the boyfriend of his former girlfriend was looking for him near his home, told his father about the matter and both ganged up to attack the man.
Chionh Boon Seng, 49, and his son also assaulted a second man, who was the friend of the former girlfriend.
Full-time national serviceman Chionh Ze Xing, who turned 20 last month, was sentenced to 18 months' probation and ordered to perform 120 hours of community service yesterday after pleading guilty in September to two counts of assault.
He assaulted the two men while on probation for earlier offences involving illegal moneylending.
His parents were bonded for $5,000 to ensure his good behaviour for his latest brush with the law.
The father was convicted and sentenced last year for his role in the assault on May 29, 2016. Court documents did not reveal details about his sentence.
The court heard that student Aaron Teo Jin Wei, 20, was the boyfriend of Chionh Ze Xing's former girlfriend, while tattoo artist Yang Ziyi, 29, was her friend.
After receiving a phone call from Mr Teo at around 5.30pm that day, Chionh Ze Xing left his flat to meet the student, who was waiting for him at a badminton court near Block 115 Teck Whye Lane.
Soon after, Chionh Boon Seng retrieved a 91cm wooden pole and joined his son.
Deputy Public Prosecutor Darshini Ramiah told the court that Chionh Ze Xing then approached Mr Teo aggressively and the student explained that he had not come for a fight.
Despite this, Chionh Boon Seng came forward and hit Mr Teo with the pole.
The pair then rained blows on the student.
Mr Yang, who was nearby, heard the commotion and came over to help Mr Teo.
The two attackers then turned their attention on the freelance tattoo artist and assaulted him. Mr Yang managed to run away from the pair and hid in a nearby carpark.
The police were notified and the two victims were taken to Ng Teng Fong General Hospital.
Mr Teo suffered injuries including facial fractures and bruises on his right forearm, while Mr Yang had a head injury and a bruise on his forehead.
For each count of assault, Chionh Ze Xing could have been jailed for up to two years and fined up to $5,000.