Pol Col Prayong Khotsakha, the Tak Bai police chief, said the home-made bomb went off about 10.15am at a sentry booth in front of the Taba customs office on the Thai-Malaysian border. It was remotely detonated.
The improvised bomb, weighing about 5kg, had been buried there and exploded as many people were going through customs procedures.
The explosion wounded Chief Warrant Officer Montri Songsriboonsit, 40, of the 2nd Border Defence Company, and Jeh Sani Che-wae, 56, a villager.
Police were investigating.