Police said the four defence volunteers from Tambon Prachan were guarding Ban Bukoh School in the tambon when the insurgents arrived in army uniforms.
They pretended to be soldiers visiting the post before they opened fire, the authorities said
The insurgents then took four HK-33 rifles and fled the scene without harming the teachers and students.
They also left road spikes behind to try to slow down the authorities that might try to hunt them, the police said.
The four were identified as Sulaiman Wae-useng, Muhammad Teteng, Abdulloh Saleh and Buaraheng Ji.