Two foreigners were called in for questioning in Bang Lamung district on Sunday night in connection with the disappearance of German property broker Hans Peter Ralter Mack.
The two foreigners, whose nationalities and identities were not disclosed, were accompanied by their lawyers.
Police said the two declined to give statements, saying their lawyers would represent them.
Later on Sunday night, police searched a house in Chok Chai Garden 2 housing estate in tambon Nong Prue. The house belonged to one of the suspects. Police did not find anything suspicious in the house.
Sources said investigators had found suspicious financial transactions totalling about 2 million baht which might be linked to the man's disappearance.
Mr Mack, 62, has not been seen since July 4. His Thai wife, said he left their home in Pattaya in his Mercedes Benz to meet a foreign property broker he had recently met.
The family filed a missing person complaint with police on July 5 and later offered a reward of 3 million baht for information on Mr Mack's whereabouts, and 100,000 baht on his car.
The silver Mercedes-Benz E350 was found by police on Sunday morning in the CC Condominium parking lot in tambon Nong Prue. The interior surfaces had been wiped clean.
