A recalcitrant offender returned to a life of crime again last year, more than three decades after his first brush with the law.

Former minimart cashier Tang Hian Leng had only just finished serving a 12-year spell of preventive detention for robbery - which came with 12 strokes of the cane - when he began reoffending.

The 47-year-old will now spend seven more years behind bars after he was sentenced to preventive detention again yesterday.

He pleaded guilty in April to criminal breach of trust, assault, verbally abusing a public servant and cheating a sex worker while posing as a policeman.

Preventive detention, which can last seven to 20 years, is for recalcitrant offenders. They must serve the full sentence with no reduction for good behaviour.

Tang engaged the services of a sex worker on Oct 21 last year before lying to the 25-year-old Chinese national, claiming he was a policeman.

He asked the woman to return the $100 he had earlier given her as it was so-called "government money". The woman complied as she believed him. Tang later asked her to have sexual intercourse with him again, the court heard.

The Chinese national agreed as she thought he would take action against her if she failed to comply.

After Tang left, she thought over the incident and alerted the police the next day, after realising that he could have deceived her.

Besides this incident, Tang admitted that he misappropriated more than $4,000 in cash from a minimart he worked at in Bukit Batok in July last year.

He also assaulted a 36-year-old man at Block 371 Bukit Batok Street 31 about a month later, punching him in the face following a dispute over a woman.

While remanded at Changi Prison Complex on Jan 19 this year, Tang became agitated and verbally abused a police station inspector who had turned up to serve some charges and record a statement from him.

The court heard that Tang first tangled with the law when he was just 15 and was given two years' probation for theft. He was in and out of jail after that for offences including molestation and criminal intimidation. In 1998, Tang was given five years' corrective training for trespassing and theft. Corrective training is a prison regime for repeat offenders without the usual one-third remission for good behaviour.

Yesterday, District Judge Ow Yong Tuck Leong said Tang was a recalcitrant offender who had shown a "blatant disregard for the law".

Tang was visibly agitated after his sentencing and, as he was led out of the courtroom, he exclaimed in Mandarin: "You did not give me a chance."