All are in Bangkok where they are undergoing further questioning. They were apprehended by police from the Narcotics Suppression Bureau on Wednesday and were taken to the capital from Phuket on Thursday.
Drug police first swooped on Joseph Manuel Hunter, a 47-year-old American, at the Phuket Country Club. He was pointed out to them by US Drug Enforcement Agency officials at the golf club in Kathu district.
A warrant for his arrest was issued by the New York Southern District Court on July 17, according to Pol Gen Priewphan Damapong, adviser to the bureau chief.
The sources said Hunter arrived in Thailand through Phuket airport on Sept 6 and had stayed on the island since.
The US embassy was advised of his trip to Thailand and contacted Thai authorities.
Authorities cancelled his Thai visa on the recommendation of the Immigration Bureau on Sept 19.
Deputy national police chief Somyot Pummanmuang said in Bangkok on Thursday that Hunter entered Thailand from the Philippines.
The sources said Thai investigators had worked closely with the USDA in a highly classified operation. Phuket police units and officials were not informed about the operation, the sources added.
Hunter was immediately taken to a house at Kathu Thani estate for interrogation after his arrest. The same team of police and investigators then searched for additional suspects in the case in the Patong beach area, leading to the apprehension of five more people.
All six suspects - including two Brits, a Slovak, a Filipino and a Taiwanese - have been named in a US arrest warrant and were expected to be deported to New York, where the warrant was issued, Pol Gen Somyot said.
He did not give a time frame for the transfer.
He called Hunter a "leading drug lord" wanted for drug smuggling, trafficking and other international crimes, which he did not specify.
"This group was considered to be a big network that spanned many countries", including Thailand, Myanmar, Singapore, Malaysia, Indonesia, Taiwan, Hong Kong and the Philippines, Pol Gen Somyot said.