A police captain at Sutthisan station in Bangkok was arrested on Monday night and later sacked for allegedly procuring illegal drugs for sale via mailed parcels.
His bosses also face an investigation.
Pol Capt Samphan Jantason, deputy inspector-general for crime suppression at the police station, was arrested when he arrived for work about 7pm on Monday. Arresting officers had a warrant issued by the the Criminal Court the same day.
Pol Maj Gen Yingyos Thepjamnong, a narcotics suppression commander, said Pol Capt Samphan is accused of procuring illicit drugs for other people to send via mail, but had denied all charges. Two alleged accomplices were arrested on April 22.
On that day, police from the Narcotics Suppression Bureau arrested Anusorn Tongsawang at Candy Post and Pay shop in Huai Khwang district with two parcels containing drugs. A subsequent search of his room at Khanittha Mansion in the same district found more drugs. A Myanmar woman identified as Ie Kongkham was also there.
Police seized at toal of 11.52 grammes of crystal meth, 50.38g of ketamine, six ecstasy pills and six methamphetamine pills from the couple. Mr Anusorn alleged that he received the drugs from Pol Capt Samphan.
Pol Capt Samphan, 38, was quoted as saying he knew the suspect because he frequently visited an entertainment venue run by Mr Anusorn. He also said about 100,000 baht found in his bank account came from an informal loan scheme known as share, a chit fund.
Deputy police spokesman Pol Col Krisana Pattanacharoen said on Tuesday that Pol Capt Samphan was "dismissed for now" from the force pending further investigation. His superiors at Sutthisan station would also face an inquiry over their supervision of their subordinate.
National police chief Chakthip Chaijinda was aware of the case and ordered decisive action and the arrest of all accomplices because a police officer committing crime was not to be tolerated, the deputy spokesman said.