A tenant of a Circuit Road flat rang his landlord and told him he was going on a business trip for a few days.
Two days later, the landlord let himself into the rented bedroom to check on it, and saw someone he thought was his tenant apparently asleep on the bed, reported Chinese evening daily Lianhe Wanbao.
The landlord then went out to dinner but came back later to find that the person had not moved.
Pulling back the blanket, he realised it was actually a 28-year-old woman who sometimes stayed over and that she was dead.
The police have classified the case as unnatural death.
A police spokesman said they received a call at about 8.30pm on Tuesday, and found the woman lying motionless in the third-floor unit in Block 70, Circuit Road. She was pronounced dead at the scene.
No arrests have been made, and investigations are ongoing.
A check by The Straits Times yesterday found the unit locked and its windows closed.
Neighbours said police officers had come knocking on doors the night that the death was reported by the landlord. They said they had not heard any commotion.
They also told The Straits Times that the tenant had moved in last year, and that the woman was his girlfriend.
"I saw her sometimes but I didn't know her well," said a woman who lived several doors away. She declined to be named, saying: "We keep to ourselves here."
Another neighbour, who wanted only to be known as Madam Neo, said: "I remember when they moved in because there was a lot of renovation around that time, but she didn't really interact with us and I didn't see her much."