A man flew into a rage when his drinking buddy's acquaintance joined their table.
Toh Kai Seng, 63, punched Mr Teo Teck Hock in the face, knocking him to the ground - a blow which ended his life.
Toh was jailed for 34 weeks yesterday after pleading guilty to assaulting 44-year-old Mr Teo.
Deputy Public Prosecutor Quek Jing Feng said Mr Teo was on his way home from a supermarket with his 12-year-old son when they walked past a coffee shop at Block 639 Punggol Drive at 3.45pm on Nov 11, 2016. He spotted three acquaintances having beer there and decided to join them while the boy went home alone.
Meanwhile, Toh was sitting two tables away with another of Mr Teo's acquaintances, Mr Lim Seng Ban. The court heard that Toh and Mr Teo did not know each other.
About two hours later, Mr Teo went over to Toh's table to talk to Mr Lim. By then, Mr Lim and Toh had downed seven bottles of beer, said the DPP.
He added: "They shouted at the deceased and asked him to leave their table. The deceased... was unhappy about being asked to leave. He continued to grumble loudly and gestured at the accused and Lim.
"Lim became angry... Lim and the deceased argued and challenged each other to a fight."
Toh stepped in and punched the left side of Mr Teo's face, knocking him backwards. He hit his head on the ground and remained motionless. An onlooker alerted the police and an ambulance took Mr Teo to Changi General Hospital.
He was placed on life support but his condition deteriorated and he never regained consciousness.
He was pronounced dead in the early hours of Nov 13, 2016.
An autopsy report stated that he died of extensive head injuries.
For assault, Toh could have been jailed for up to two years and fined up to $5,000.