
The bomb was hidden near a small garden in the school ground and set off remotely as the three soldiers were in range.
Separately, in Narathiwat's Chanae district, gunman shot at an election campaign staff of the Chart Thai Pattana Party candidate, severely injuring the person.
The shooting took place at 10 am on the Ragnae - Chanae Road in Lubo Lasoh village in Tambon Phadungmatra of Chanae district.
Hawaetah Tahyeh, 51, was shot three times on his chest and once on his neck by a gunman using AK-47 assault rifle.
Hawaetah took part in the election campaign for Niaris Jetapirom, who is contesting in a by-election in Narathiwat's Constituency 2.
Hawaetah rode in a pick-up truck of the 15-vehicle campaign procession. His pick-up truck was the last in the procession. Police said insurgents in a pick-up truck sped up past the procession and opened fire at Hawaetah.
The Tuesday attacks came one day after Abhisit announced the formation of a new agency to oversee the three southernmost provinces.
The new civilian-led agency will directed by a C-10 bureaucrat and have the power to transfer any government officials from the region.
It is not clear as to how the already complex security apparatus in the deep South will realign itself under the new agency.
Successive Thai government have provided the military with overwhelming mandate extending beyond traditional security to include development and reconciliatory effort.