A secondary school teacher who used two counterfeit $100 notes he had made to pay for massage services began his three-year jail term yesterday after losing his appeal.

Daniel Wong Mun Meng, 44, failed to convince a High Court judge that the notes were intended as a teaching tool to "excite and engage" his students on the topic of currency exchange.

His contention that he wanted to use the notes as props for the school's Maths Day, because they depicted youth from uniformed groups and were in line with the event's SG50 theme, was rejected.

In dismissing Wong's appeal against conviction for counterfeiting the money and using the fake notes as genuine currency, Justice Aedit Abdullah said his reasons beggared belief.

In late July 2015, Wong made the two fake notes by photocopying a genuine one on his home printer.

On the night of Aug 3, 2015, he drove to Orchard Towers, where he offered to pay a Vietnamese woman $200 for "services". He paid Ms Nguyen Nhu Trang with the fake notes before driving her to Fragrance Hotel in Balestier Road. They spent about an hour there.

He testified in court that she gave him a full body massage and then had sex with him. But Ms Trang told the court that no sex was involved.

The case came to light after she tried to use one of the fake notes at a supermarket and was caught by a cashier.

Police officers arrested Wong at Bukit Batok Secondary School on Aug 20, 2015. He was suspended from teaching duties in December the same year.

Wong was found guilty after a 12-day trial and sentenced to three years' jail in November last year. He had been out on bail pending appeal.

Yesterday, his lawyer Melanie Ho argued that he should be cleared of the charges. She pointed to the scheme of work for Wong's class to establish that he did intend to deal with currency exchange as a topic.

But the judge questioned whether this really substantiated Wong's reason for producing the counterfeit notes or provided an excuse for him.

"Do teachers generally create counterfeit notes to fulfil the scheme of work?" he asked, adding that Monopoly money or other currency could have been used.

Ms Ho argued that three years was too harsh for Wong. She added that his infidelity has taken a toll on his marriage.

Deputy Public Prosecutor Kenneth Chin said Wong's defence was an afterthought, adding he failed to mention any intention to use the fake notes for class or for Maths Day when questioned by the police.