An ex-navy engineer admitted booking an escort through a pimp but claimed he had no idea she was only 17.
Kwa Wee Nam, 34, also told a court that the minor in question never showed up and that a different, older escort went to his hotel to fulfil the teenager's booking.
But prosecutors shot down his "contrived" story in a four-day trial and Kwa became the second man, after Swiss banker Juerg Buergin, to be convicted of commercial sex with a minor in the online vice ring case after claiming trial. He was sentenced to four months' jail.
District Judge Liew Thiam Leng convicted Kwa of paying $450 for the underage girl's sexual services at Hotel 81 Bencoolen on Oct 8, 2010.
Deputy Public Prosecutor Winston Man argued that Kwa's defence was "at best, an afterthought".
Text messages on the phone of the 35-year-old escort, who Kwa claimed replaced the minor, showed she was unable to accept bookings and serve any clients on the day in question. The escort, who also worked as a secretary, testified that she had never seen Kwa before and had no impression of him.
Under cross-examination, she also said that she did not know the minor or any other of the escorts working for Tang Boon Thiew, the pimp.
Tang testified that it was absolutely not his practice to "bait and switch" - promising a particular escort to a client but ultimately sending another to take her place.
When queried why, he said it was "stupid" to ruin his business as clients would not go back to him upon finding out about the deception.
The underage escort had testified that between September 2010 and February 2011, she served around 60 clients and had sex with all except six of them.
Buergin, 42, a former executive director with UBS, was jailed for four months and three weeks on two charges of commercial sex with the minor. A total of 51 men, from all walks of life, have been charged with having commercial sex with the same girl.
Kwa, who was defended by Mr Edmond Pereira, could have been jailed for up to seven years and/or fined.
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