A man and his girlfriend were arrested on charges of printing counterfeit US, Lao and Thai banknotes in Bang Khen district, Bangkok, after a three-month investigation sparked by a request from the US Treasury.
Police raided a one-unit, three-story shophouse on Watcharapol Road on Friday.
On the first floor they found a printing press, plates for US, Lao and Thai currency notes, and a large number of what appear to be printed samples of Korean and Lao banknotes.
Rames Phrasubin, 49, of Yasothon province, and Walaiporn Nuchsawasdi, 32, of Phetchaburi province, were on the premises, and were arrested.
On the second floor, police found two pistols and two boxes of ammunition. They also seized a Nissan Terano vehicle registered in Bangkok. They did not find any counterfeit US currency.
Pol Maj Gen Sommai Kongwisaisuk, deputy commissioner of the Central Investigation Bureau, said Treasury officials in the United States had asked Thai police to find the counterfeiters who were making forged dollar banknotes that were found in circulation in the US.
A three-month investigation had led them to the printing shop in Bang Khen.
He said Mr Rames ran a normal printing business, producing documents, books and items such as donation envelopes.
He would also take orders for counterfeit banknotes, which he would print and deliver immediately in the seized Nissan.
Pol Maj Gen Sommai said the forged Lao currency was sent to Laos and used to pay workers there.