Police arrested suspected members of a call centre gang in Sungai Kolok district in Narathiwat province on Saturday.
Pol Lt Gen Jirabhop Bhuridej, Chief of the Central Investigation Bureau, said the CIB worked with the Crime Suppression Division Subdivision 6 and local police to raid a house in the district, which borders with Malaysia.
The suspects were identified as Sarina, a 24-year-old local woman, and Malaysians Kiang Wan, 25, and Kuok Rong, 36.
Police also seized 15 Sim boxes and GSM gateways and three WiFi routers during the raid.
Pol Lt Gen Jirabhop said one Sim box, priced at about 100,000 baht, can call 480 potential victims at one time.
The suspects are accused of using unauthorised radio communications equipment and running an illegal telecommunication business.
One suspect, Mr Wan, is also accused of illegal entry to Thailand, according to Pol Lt Gen Jirabhop.
Police said Ms Sarina and Mr Wan, accepted the charges, saying they worked as house caretakers under a Malaysian employer, and used their salaries to rent a house and buy the equipment.
Mr Rong, however, denied the charges, saying that he merely transferred money to Ms Sarina without involving himself in the scam, police said.
Police will expand the investigation into the gang, said Pol Lt Gen Jirabhop.
The raid in Narathiwat followed an investigation into unauthorised GSM gateway installation for call centre scams in the province, he said.
This particular gang used a Sim box technique to divert international calls to a cellular device via the internet.
To do so, he said the gang had used Sim Bank, hardware capable of reading a bank for Sim cards, to communicate with GSM gateways installed in other places via a cloud server.
The gateways then transferred the internet signal into a cellular signal, as indicated by the local country code displayed on the victim's mobile screen, he said.
Doing so can help the scammer get away with violating the National Broadcasting and Telecommunication Commission's (NBTC) regulation on telephone prefixes, he said.
Both Sim Bank and GSM gateways are expensive tools that need NBTC authorisation before they can be used, he said.
