The six injured were among 12 defence volunteers riding on two armour-plated pickup trucks on their way back to base in Mai Kaen district from a training centre in Tambon Tha Sab, Muang district.
As the two pickup trucks were approaching a motorcycle with a side car rigged with about 50 kgs of explosives stuffed in a 15-kg gas canister which was parked on the roadside, the two drivers became suspicious and swerved their vehicles toward the other lane of the road in Tambon Nong Hoi, Kapor district.
Suspected militants who had been waiting in the bushes a safe distance from the parked motorbike then detonated the rigged bike, causing a loud explosion. The force of the blast damaged the second vehicle and injured six men on board.
The first pickup truck escaped undamaged and its driver and passengers were safe.