Pol Lt-General Sanit Mahathavorn said that Pol Sergeant Pissanupong Ngamtura was nabbed in the parking lot of a condominium on Sukhumvit Soi 77.
Police said that Pissanupong allegedly got the "ice" from a major agent in the northern region and distributed it to customers in Bangkok.
Following a tip-off, police followed him into the parking lot and he was apprehended after a search uncovered the drug.
A search of his apartment in the building found two handguns. His testimony led to the arrest of two other suspects who are Chiang Rai natives.
He claimed the other two suspects owned the drugs and he was just a distributor.
He will face a disciplinary investigation by a panel set up by Traffic police commander Pol Maj-General Jirasan Kaewsang-ek. He joined the traffic police force on December 1, 2016.
Sanit said he has already ordered senior police officers to improve the behaviour of their subordinates.