A roadside device struck a pick-up truck carrying a group of seven villagers in Narathiwat province’s Ra Ngae district and then unknown gunmen opened fire.
“A team of soldiers went to the area to rescue them but militants triggered a second explosion,” injuring two troops, a police officer in Ra Ngae told AFP by telephone.
Thailand’s southernmost provinces have been plagued by more than eight years of conflict that has claimed the lives of more than 4,800 people, both Muslims and Buddhists.
People in the region complain of a long history of discrimination against ethnic Malay Muslims by authorities in the Buddhist-majority nation, including alleged abuses by the armed forces.
Attacks have become more frequent and intense in recent months, observers say.
On October 25, 15 explosions blamed on suspected Muslim rebels ripped through a town in neighbouring Yala province, killing at least one civilian and wounding dozens more.
That attack coincided with the seventh anniversary of a protest in the region that left 85 anti-government demonstrators dead, most of whom suffocated or were crushed to death while being transported to a detention centre.
Rights groups have said the failure of Thai authorities to hold security forces to account over the deaths has fuelled further violence and alienation in the southern region bordering Malaysia.
On Sunday a dozen small explosions shook five districts of Narathiwat province but there were no serious injuries, hours after gunmen shot dead three Buddhists at a petrol station.