Ministry spokesman Sek Wannamethee said on Wednesday that officials at the Thai Embassy in Tokyo have offered assistance to the ex-Thai metropolitan police chief.
Some of the officials work as interpreters for him, while others recommend lawyers to ensure justice.
According to the spokesman, the incident is being investigated and Thai officials must wait for Japan's legal procedures, while the Thai Embassy in Tokyo will do the best to facilitate matters to ensure that Pol Lt Gen Khamronwit is treated fairly in accordance with laws.
Japanese police arrested the former Thai metropolitan police chief for carrying a pistol and ammunition on his way to board a plane back to Thailand in the evening of June 22.