A company managing director smashed a glass against a man's head in a pub after the victim chided him for trying to steal other patrons' drinks.
Briton Sam Joseph Chapman, 28, later received 12 stitches behind his left ear.
For the offence, Frenchman Franck Louis Maurice Peltier, 51, who used to work for financial data management company Asset Control, was yesterday jailed for three weeks. He pleaded guilty to causing hurt to Mr Chapman at the Employees Only pub in Amoy Street at around 12.20am on Dec 22 last year.
One count of outraging a woman's modesty at the same nightspot about 20 minutes earlier was taken into consideration during sentencing.
Peltier had gone to the bar at around 11pm on Dec 21 last year to celebrate after winning a contract. He bought drinks for some of the other patrons, including Mr Chapman.
Deputy Public Prosecutor N.K. Anitha said: "The accused was observed to be flirting with others at the pub and (used) an extended straw - by connecting two straws together - to fish out drinks from others at the bar counter.
"When the accused put the extended straw into a bottle near the victim, the victim took the straw out and threw it away, across the bar."
Peltier repeated the stunt and received a similar response from Mr Chapman, who told him that it was wrong to steal drinks from others.
When Mr Chapman turned away to face his friends, Peltier grabbed a glass from the bar counter and smashed it against his head. He also punched Mr Chapman, causing him to fall forward.
The Briton did not retaliate and the police were notified.
An ambulance took him to the Singapore General Hospital, where he was found to be suffering from a wounded scalp and a bruise near his collarbone.
DPP Anitha urged District Judge Carol Ling to jail Peltier for at least three weeks, stressing that the Frenchman had hurt a vulnerable part of Mr Chapman's body.
Peltier's lawyer, Mr Godwin Campos, asked for his client to be sentenced to either a heavy fine or not more than a week's jail.
He told Judge Ling that the Frenchman had thought he was entitled to help himself to the other patrons' drinks as he had bought some for them.
Mr Campos also said that his client had acted out of character and that the offence was not premeditated.
Peltier, who was based in Singapore, was made redundant in January this year, the court heard.
For causing hurt, he could have been jailed for up to two years and fined up to $5,000.