Sandy Winick, 55, was caught in his room at Empire Place in Yannawa district by Special Branch police and is now awaiting extradition to the United States, the source at the police unit added.
Another Canadian expat wanted in connection with the scam, Greg Curry, 63, is believed to have fled Thailand, according to the source.
Mr Winick and Mr Curry were among nine Canadians and Americans indicted by the US Attorney's Office on charges of cheating investors in about 35 countries out of more than $140 million (4.4 billion baht).
Six of them appeared in US federal courts in New York's Brooklyn, Miami, Los Angeles and Tucson, Arizona, last week.
A seventh suspect was arrested in the Canadian province of Ontario.
The source said Special Branch police and the Federal Bureau of Investigation had been tracking Mr Winick for some time and asked the Criminal Court to approve an arrest warrant on Friday after they pinpointed his whereabouts. The FBI's wanted poster for Mr Winick said that during the past three years he had lived in Thailand, Hong Kong, China, and Vietnam
Mr Winick had been arrested in 2011 by the Crime Suppression Division on fraud charges, after setting up a Thai call centre to lure victims from other countries into scams, the source said, adding that the Canadian was also charged with illegally working in Thailand. But he jumped bail and left the country, before sneaking back into the kingdom again.
Mr "Winick’s track record in business includes bankruptcy filings, a dizzying number of subsidiaries and companies that traded over-the-counter, and co-founding testosterone-laden cable channel Fight Network, which features boxing and mixed martial arts," according to the Toronto Star newspaper.
Others arrested in what US officials called one of the biggest international penny stock frauds ever investigated are Kolt Curry, 38 and Gregory Ellis, 46, both Canadians from Ontario; and Americans Gary Kershner, 72, of Arizona, Joseph Manfredonia, 45, of New Jersey, Cort Poyner, 44, of Florida, and Sonkram Roy Sahachaisere, 43, and William Seals, 51, both of California, AFP reports said last week.
According to the indictment against them, the defendants fraudulently "pumped up'' the share price of worthless penny stocks and then "dumped'' billions of shares of those stocks by unloading them on unsuspecting investors worldwide.
The defendants allegedly sold shares in worthless shell companies as well as collecting bogus regulatory and legal fees related to the phony stock.
If convicted, the accused could face up to 20 years of imprisonment for each count of conspiracy to commit wire fraud, as well as up to five years for conspiracy to commit securities fraud.
They also allegedly operated "boiler room'' call centres in at least four countries that induced penny-stock investors to pay advance fees that the defendants promised would enable them to sell their stocks and recover losses. In fact, the fees were stolen.
The penny stocks involved included companies such as Resource Group International, a Wyoming corporation based in Thailand that says it developed a revolutionary fertiliser, and RainEarth Inc., a Nevada corporation based in Beijing that says it is in the mineral-exploration business and developing a specialised fibre, according to prosecutors.
If convicted, the nine face up to 20 years in prison for each count of conspiracy, wire fraud and securities fraud, as well as time behind bars for impersonating an agent of the Internal Revenue Service, the US tax collection agency.