The attack occurred at 11:40 am at a bridge in Nambaeng village in Tambon Praiwan in Takbai district.
Police said insurgents hid the bomb, weighing about 50 kilogrammes inside a cooking gas cylinder left on a motorcycle with side-carriage at the bridge.
Insurgents detonated the bomb with a walkie-talkie when the buss transporting about 40 rangers arrived at the scene.
The Nation