A manhunt has been launched for a gunman who allegedly killed a highway police officer and seriously injured another following a promotion discussion that occurred in Nakhon Pathom province late on Wednesday night.

Police had been deployed to various spots in Nakhon Pathom and nearby provinces to search for the suspected gunman.

Police have identified the suspect as Thananchai Manmak, 45, who is believed to be a henchman of Praween Chankhlai, alias Kamnan Nok, a tambon chief.

The incident took place at about 10pm in front of a house in tambon Takong of Nakhon Pathom.

According to a witness, Kamnan Nok invited a group of highway policemen to his house for a dinner meeting. Two of the officers in the group were Pol Maj Sivakorn Saibua, chief of highway police station 1 under the Highway Police Sub-division 2, and Pol Lt Col Wasin Panpee, deputy commander of the Highway Police Sub-division 2.

During the discussion, Kamnan Nok tried to persuade the officers to promote his nephew, a highway police officer who was under the supervision of Pol Maj Sivakorn. However, Pol Maj Sivakorn disagreed.

The tambon chief had a heated argument with the officers and eventually stormed off. Shortly afterward, a man approached their table, pulled out a gun and opened fire. The gunman was later identified as Mr Thananchai.

Pol Maj Sivakorn sustained seven gunshot wounds and later died. Pol Lt Col Wasin was shot in the left arm and was admitted to a hospital.

Police said the gunman committed the crime in full view of many people who had been invited to the dinner. There were altogether five dining tables, one of which was reserved for the group of highway police.