District Judge Kessler Soh told former project engineer Waduge Buddhika Upashantha Fernando, 38: "What you did was abhorrent. You must not commit such offences again."
The married Singaporean, who is originally from Sri Lanka, pleaded guilty in June to one count of non-consensual sexual penetration.
He committed the offence at his Kim Keat Avenue flat in Toa Payoh where he lived with his family. It was not stated whether they were at home at the time.
His tenant, a 28-year-old Malaysian cook, had lived in the unit for about four months before the incident.
The victim had little interaction with the other members of the household, as he was usually out of the flat by 9am and back only at 11pm every day.
Deputy Public Prosecutor Marshall Lim said that on Nov 10 last year, the victim returned to the flat at around 11.30pm and fell asleep in his room about 1½ hours later.
Fernando returned home at around 3am and was about to head out again to a nearby market when he felt an urge to have sex with another man.
The tenant woke up about 10 minutes later and saw Fernando committing the offence.
DPP Lim said: "The victim yelled and kicked at the accused instinctively... The accused left the room and then left the flat immediately. The victim was shocked and did not know how to react."
The cook then alerted the police about an hour later.
The prosecution had urged Judge Soh to sentence Fernando to six years' jail with three strokes of the cane.
The DPP added: "This is the place where one can expect to feel safe and secure. When penetrative sexual assault involves landlords and tenants who share the same premises, it will undoubtedly cause grave public disquiet."
Fernando's lawyer, Mr Amolat Singh, pleaded for a five-year jail sentence for his client. He told Judge Soh: "He did not use any violence or any force or any stupefying drug to overcome the victim's resistance or to obliterate his memory.
"There was no moral corruption nor is there any evidence that the victim suffered grave psychological or emotional trauma."
For performing the unconsensual sexual act on the cook, Fernando could have been jailed for up to 20 years and caned.
(Excerpts : straitstimes.com)