A nephew of Deputy Interior Minister Chada Thaised was arrested and crystal meth, a gun and ammunition seized at a hotel in Bangkok's Huai Kwang district on Monday night.
Detectives of the Metropolitan Police Bureau arrested Norased Thaised and another man and two women found in the same room at the hotel about 10pm on Monday. The hotel's name was not released.
Police also found six packets of crystal methamphetamine, known as "ice", in the room along with an 11mm pistol and six rounds of ammunition.
Mr Norased was charged with illegally possessing and using the drug and illegally carrying a firearm and ammunition. The three other people were identified only as Kijja, Walit and Anchaleeporn.
Police said the arrest followed a complaint about a drug-abuse party.