Undeterred that he had spent almost half his life behind bars already, a man risked a five-floor drop to climb through a bedroom window and try to force himself on a woman who had spurned his advances.

On Monday, Razali Osman, 43, was sent to jail for 20 years and ordered to be caned 24 strokes for sexual assault, attempted aggravated rape and housebreaking.

"A serial rapist, that's what you are," said Justice Chan Seng Onn in sentencing him. Razali was last sent to jail in 1993 for raping three women, including his girlfriend's sister, and robbing two of them.

He was released from prison in February 2012. He moved in with his sister and became interested in her tenant, a 31-year-old foreigner working here, but she turned him down as she had a fiance back home. One night in October 2012, he climbed out the living room window of the fifth-floor flat and into the window of her room. Once inside, he violated her and tried to rape her but eventually stopped.

The woman later made a police report and moved out.

As a result of the attack, she became wary of men and this led to her breaking off her engagement a few months ago.