A transsexual who performed oral sex on a 15-year-old boy was jailed for 15 months on Wednesday.

The long-haired and bespectacled Tan Yeong Perng, 36, had admitted earlier to the sexual offence in the storeroom of a 7-Eleven store in Upper Thomson on Jan 8, 2011.

A district court heard that he was working as a store assistant and cashier when the victim came to the convenience store at around 2am to buy pancakes.

Tan, who underwent breast implant surgery in Thailand in 2004, cross-dresses as a female and wears make-up, asked the student his name, age and where he lived. Not wanting to reveal too much as Tan was a stranger, the victim revealed his age among a few other bits of information.

While waiting for the pancakes to be ready, Tan went to the toilet to touch up his make-up, came out and asked the victim to follow him into the storeroom so he could have a "private conversation'' with him.

Inside the storeroom, he started kissing the victim and tried to pull down his shorts. He then committed the obscene act.

The victim felt something was amiss when his leg accidentally brushed against Tan's groin, and realised that Tan was actually a male.

He was in a state of panic and shock and tried to pull away from Tan, who bit his private parts. The victim eventually managed to pull away from Tan, pulled up his shorts and ran out of the store.

His mother noticed his strange behaviour and asked what was wrong. The victim cried and told her what had happened. She called the police.

A second charge of molesting a 19-year-old male in January last year was considered during his sentencing.