FAKE $100 notes have surfaced thrice in the past month.
Two of them even bear the same serial number.
Last month, the fake notes were used at a Chinatown art stall and an Orchard Road ice-cream stall.
Then, on Thursday, a man was issued one such note by a bank branch in Tampines, reported Shin Min Daily.
He gave the note to his friend as payment for a purchase.
But when the friend used the money at a store in Hougang, the alert shopkeeper raised the alarm.
The friend, who gave his name only as Mr Ho, said: 'I was talking on the handphone when the shopkeeper told me the note was fake. I was so shocked.
'I felt very embarassed and quickly gave him another note as payment.'
BANK CONFIRMS FAKE
Shaken, Mr Ho, 34, took the note to an officer at a nearby bank, who confirmed that it was indeed fake.
On closer inspection, the watermark-likeness of former Singapore president Yusof Ishak was blurred, as was the kinegram - the silver octagon.
The colour was also slightly different from the real thing.
So on Friday morning, Mr Ho and his friend reported the matter to the Tampines bank branch which issued the fake note.
Their statements were taken, and the bank replaced the note with a genuine one.
The bank spokesman has confirmed that the customers made a report and that the bank exchanged the note out of goodwill, reported Shin Min Daily News.
The bank is also working with the police. It has handed over the note for investigation.
But it was only after Mr Ho met the Shin Min Daily reporter that another startling fact came to light.
The $100 note's serial number - OAR500930 - was found to match an earlier case.
On 12 Dec last year, an ice-cream vendor at Orchard Road got a fake $100 note with the same serial number.
A man had used it to pay for seven ice-cream wafer biscuits.
As it was dark, the 55-year-old vendor didn't examine the note and gave him $93 in change.
It was only later that he realised he had been duped.
On 10 Dec last year, a woman at a Pagoda Street stall in Chinatown selling art pieces was also fooled.
A man had approached her to 'break' his $100 note so he could buy magazines at a nearby stall.
She agreed, and gave him two $50 notes only to discover that the note was fake later.
Last May, a customer paid for a $22.05 fish curry dinner at a Far East Plaza restaurant with a fake $100 note.
The fake note was discovered by the restaurant manager who was counting the takings before visiting the bank.
There were 10 cases of counterfeit money involving local and foreign currency in 2005, up from two cases in 2004.
The act of counterfeiting money or trafficking in it carries a possible life term in jailand a fine.