A Singaporean man has been sentenced to nearly four years behind bars after attempting to frame his estranged wife by placing cannabis in her car, knowing she could get the death penalty.

Tan Xianglong, 37, was sentenced at a district court on Thursday to three years and 10 months in jail, court documents showed.

The couple had been estranged for less than two years, after having sought a divorce but failing to get one immediately because of the short duration of their union, the documents said.

Tan had been angry at his wife because he thought she did not contribute enough financially to the marriage.

He consulted lawyers and came away with the idea that a divorce could happen if one of the parties had a criminal record, the documents said.

He initially hired a private investigator to gather evidence she was committing adultery, but no proof was found.

This prompted Tan to hatch the scheme to frame his estranged wife by planting weed in her car - describing it to his girlfriend as a perfect plan.

Tan bought the drugs on the black market and weighed them at home, finding they came in at 510 grams (18 ounces) - more than the 500-gram threshold that merits the death penalty in Singapore.

From his research online, he knew that the involved party (his wife) would face the death penalty if convicted of trafficking more than 500 grams of cannabis, the court documents said.

He nonetheless decided to proceed with his plan as he was very angry with the involved party.

A laboratory analysis of the drugs, however, showed they only contained 216.17 grams of pure cannabis.

Tans wife was arrested after police discovered the drugs in her car, but they found no other incriminating evidence against her.

Police then turned their investigation to Tan, who was subsequently arrested.

The United Nations and rights groups say capital punishment has no proven deterrent effect, and have called for it to be discontinued.

Singaporean officials, however, contend it has helped make the country one of Asias safest.

The city-state carries out the death penalty by hanging. (Channels TV)