Unhappy with his ex-wife's new lover, Low Lee Seng beat him up after the two met by chance at a clinic in September last year and got into an argument over money.
His victim, Mr Chin Chee Chung, 32, ended up in hospital with serious injuries including rib fractures and a bruised kidney, and required follow-up medical treatment for a year.
Low, 41, was on Friday sentenced to three years in jail and six strokes of the cane after pleading guilty to voluntarily causing grievous hurt. One other such charge from a separate offence was taken into consideration.
Low, who divorced his wife about nine years ago, learned of the new relationship after his release from a drug rehabilitation centre last August. He allegedly grew unhappy upon hearing of some $2,000 in unsettled debts owed to her by Mr Chin.
About a month later at the clinic off Kampong Kayu Road, Low asked Mr Chin to follow him behind the premises, where they got into an argument.
Unprovoked, Low punched his victim in the eye and continued to punch and kick him after he had fallen to the ground. The maximum penalty for the offence is a jail term of up to 10 years and a fine or caning.