A customer service officer who admitted to having sex with a 15-year-old girl corrupted her and treated her as his sexual plaything, said a prosecutor on Thursday.

Chee Wei Tong, 24, who faces 10 charges of sexual abuse, admitted to three charges committed in 2012. He is the fourth man to be convicted of having sex with the minor, who was a virgin when he schooled her in kinky sex and encouraged her to read up and learn more about it.

Deputy Public Prosecutor Sharmila Sripathy-Shanaz told the court that in the course of their sexual encounters, Chee choked and slapped the minor. He had suggested that he be dominant, and she, submissive.

The court heard that the minor created an account on OkCupid, a dating and social networking website, in mid-2012 to make more friends. She claimed she was 18 as this was the minimum age allowed for registration.

Sometime in July that year, she began communicating with Chee. She told him she was 15. Chee told her he had a girlfriend and practised polyamory - the philosophy of being romantically involved with multiple individuals at the same time.

He also revealed that he had a fetish for Bondage and Discipline, Dominance and Submission, Sadism and Masochism (BDSM).

On Aug 1 that year, she went to his flat where he had sex with her. In the midst of intercourse, he slapped her face and buttocks a few times. He also choked her, albeit lightly. She did not stop him as he had told her these were part of BDSM practices.

In the second week of August, she went to the flat at Kang Ching Road in Jurong a second time where he made her perform oral sex on him.

Their last meeting was sometime between end-August and early September when he took her to an HDB block in Punggol and had sex with her at a staircase landing despite her reluctance. As they were walking to the MRT station later, the minor told him that she wanted him to wear a condom when they engaged in sex in future.

"He refused and bragged that he had slept with over 30 women and had not, to date, impregnated any of them," said Ms Sripathy-Shanaz.

Chee will be sentenced on April 8. Three other offenders who had sex with the same girl were jailed between 10 and 12 months each. One more case is pending

The maximum penalty for the offence is 10 years' jail and a fine.