The attack occurred about 7.54am as Pol Sr Sgt Maj Montree Saengmolee was travelling in his car to work at Krong Pinang police station.
At a spot on the Malayu Bangkok - Phong Yirai bypass in Muang district, two men who had followed him on a motorcycle opened fire him.
Pol Sr Sgt Maj Montree was killed instantly. The gunshots left many holes in the car. The attackers took his pistol and a rifle from the car before fleeing.
The officer had been shot and wounded previously in an earlier attack.