Hans Peter Ralter Mack, 62, reportedly disappeared while in Chonburi's Bang Lamung district last week where he was to negotiate with a foreign broker regarding a land deal on Samui Island in Surat Thani worth more than 100 million baht.
His relatives have filed a complaint with Nongprue Police Station and are offering a reward of 3 million baht to anyone who finds the missing businessman. His car was recently found at a condominium in Bang Lamung district.
Both suspects remained silent, referring all questions to their lawyer, police said, adding that another suspect, a foreign woman, had also referred them to her lawyer.
Separately, the police team led by Pol Maj Gen Theerachai Chamnanmor, investigative chief of the Provincial Police Region 2, raided a suspect's residence in Bang Lamung district but found nothing untoward.
However, police investigators have discovered abnormalities in financial transactions worth more than 2 million baht.
Investigators are collecting evidence to see if these financial abnormaities are related to the disappearance of the German businessman.