A Pattani-based businessman; Sahachai Jiansermsin, 44, is in military court's custody on charges related to security issues.
Military officer Senior Colonel Jatuporn Kalampasut, who heads a team under the Internal Security Operations Command Region 4 that suppresses additional threats, is co-ordinating with various authorities in an attempt to solve the case.
"I can't disclose details because it's related to security issues," a source quoted Jatuporn as saying.
The officer was involved in the raid on Sahachai's company at a Pattani industrial estate on Wednesday in which fake immigration stamps and cash, including foreign currencies, were found. Sahachai was arrested later that evening.
His name had previously been linked to suspicious activities.
At a press conference two years ago, Sahachai dismissed allegations that he was involved in illegal logging and smuggled oil. He also insisted that he had never sponsored an insurgency group.
Pattani is one of the southernmost provinces that has struggled with violence for a decade.
Investigations are ongoing to determine if Sahachai is involved in smuggled oil, illegal logging, or any other illegal activities.
Sahachai owns Sahasap Tawee Khamai Limited Partnership, which is located in Pattani's Muang district.
Two years ago, members of Jatuporn's team and the Department of Special Investigation found four trucks that had been suspiciously modified to carry oil at Sahachai's firm. They also found about Bt23 million and foreign currencies.
Also two years ago, Sahasap Inter-national represented a ship owner in lodging a complaint with police after claiming pirates raided their ship in the Gulf of Thailand and stole about Bt119 million in Singapore dollars and Malaysian ringgit.
According to the complaint, the ship was en route to delivering the money to VIP customers on Losin Island in the Gulf of Thailand when the pirates struck.
An investigation by the Isra News Agency found that Losin Island is uninhabited.
Many people believe that Sahasap International is linked to Sahasap Tawee Khamai.