A HONGKONG criminal, believed to be the world's leading credit card counterfeiter, is to stand trial in the United States in connection with a multi-million dollar racket that involved fraudulent use of the cards. Tam Wai-keung, nicknamed ''Ma Chi'' or ''double finger'' because of a second thumb on his right hand, will appear in a Miami court in October charged with ''possession of access devices''. He is believed to be the mastermind of a gang which produced at least 600 fake credit cards in Macau. Police say losses of more than $46 million may have been incurred. Tam was arrested with two others during a joint operation between Hongkong's Commercial Crime Bureau, the Independent Commission Against Corruption and the US Secret Service. The operation also netted 17 members of the gang in Macau and Hongkong. Last week, a warrant was issued for the arrest of Tam's wife, Lai Hiu-chui, who is believed to be in the US. Tam and his gang used the cards to buy designer Rolex watches, Louis Vuitton leather goods, and other luxury items from shops in Europe, the Caribbean and the US. Chief Inspector Clive Tricker, who headed ''Operation Pay Sage'' into the gang's activities, said 220 counterfeit credit cards, five forged passports and 60 fake driver's licences were found in three hotel rooms in Miami when Tam was arrested. Secret Service agents also discovered 27 receipts for goods bought with the fake cards and about 1,000 account details. Inspector Tricker said Tam was believed to have led a team which operated from a rented mansion on the West Coast, where the cards were sent from Macau and where they were embossed and encoded before being used. ''They did the West Coast and then moved over and did the East Coast,'' he said. Detectives believe the gang bought US$600,000 worth of goods on the East Coast. Everything bought was then sold almost immediately. The gang, said to have previously operated under Tam's guidance in Europe and the Caribbean, also used the cards to withdraw large amounts from cash dispensing machines at US casinos. Tam, who is recognisable by his heart-shaped second right thumb, is understood to have been convicted of similar offences in Denmark, and has also been found guilty of robbery and drug offences in Hongkong. Inspector Tricker said Operation Pay Sage, which started last November, was continuing into the organisation.