The explosion occurred at 3:10 pm in Chanae district, Narathiwat when soldiers, paramilitary rangers and defence volunteers riding two vehicles were escorting to a teachers’ car travelling from Ban Ai Krot School to their residences.
Two soldiers died instantly at the blast site and the five others were injured, two of whom are in critical condition, police said.
After months of relative calm, Thailand’s south has seen increasing attacks in the past few weeks.
Hours before the blast, a Muslim man was found shot dead in his car in Sri Sakhon district. Last week, similar cases killed other four people in a 24-hour period.
Violence often takes place in southern Thailand, where several separatist groups are operating. Conflicts between the Government’s army and separatists have killed over 6,300 people, mostly Buddhist and Muslim followers, over the past decade.
Although the Thai Government pledged to speed up peace talks with separatists in the south through Malaysia in the end of 2014, little progress has seen so far.