Government officials arrested for alleged criminal involvement in the running of guns to Myanmar will also face an Interior Ministry investigation for serious disciplinary breaches.
The officials were arrested during police raids on Monday that broke up a gun running network allegedly run by Danupol "Bell" Samaesarn, former assistant village chief in Chon Buri's Sattahip district.
The Crime Suppression Division's Hanuman special operations unit enforced 16 court warrants to search premises at 21 locations - in Bangkok, Chon Buri, Kanchanaburi, Udon Thani and Chiang Mai.
National police chief Pol Gen Suwat Jangyodsuk released details of the operation on Tuesday night.
He said CSD officers arrested five suspects and seized a large quantity of illegal guns and gun parts.
Mr Danupol, 32, the prime suspect, was arrested at a house in a housing estate in Moo 4 village, tambon Phlu Ta Luang, in Chon Buri's Sattahip district.
Also in Chon Buri, police arrested Dongpol Rujithammaraj, 49, the Si Racha district chief.
Three other suspects were arrested in Kanchanaburi. They were Sawit Jiamjiraporn, 60, a former Sai Yok district chief; Kornnit Paothui, 52, a Sai Yok district official; and Yandet Iamsa-ard, 31, a defence volunteer in Sai Yok district.
Current Sai Yok district chief Neramit Luang-aramfa said he had reported the arrests of Mr Sawit, Ms Kornnit and Mr Yandet to Kanchanaburi governor Jirakiat Phumsawat.
A fact-finding committee had already been set up to investigate alleged disciplinary offences, and had found grounds to the allegations against them, he said.
According to Mr Neramit, interior permanent secretary Suthipong Julcharoen had set up a committee to conduct a serious disciplinary investigation against Mr Sawit and three other officials arrested on Monday.
The investigation result was expected soon, Mr Neramit said.
Mr Sawit became Sai Yok district chief on April 7, 2020, and retired from government service on Sept 30, 2021.
While in the position, he had handled many cases involving the smuggling of job seekers from Myanmar and encroachment on natural resources.
The operation on Monday was a follow-up to a CSD operation in 2020 in Chiang Rai and Nong Khai province, when alleged gun traders and people with large numbers of guns in their possession were arrested.
Many of the guns seized in the operation were found to be originally issued by the government with proper registration papers to officials under welfare programmes in Chon Buri's Si Racha and Kanchanaburi's Sai Yok districts.
The guns were allegedly supplied by Mr Danupol.
According to police, Mr Danupol had connections with officials, defence volunteers and member of drug suppression teams. He used their identification cars to file a request in their names with the district office for official permits to buy guns under government welfare programmes.
With the official permits in hand, guns were issued to them with proper registration. With help from some officials in Si Racha and Sai Yok districts, Mr Danupol collected the guns and supplied them to buyers in Myanmar.