The bomb only partially detonated, but still left a substantial crater.
Police said the attack occurred about 12.10pm. The eight soldiers on four motorcycles were returning to their base after delivering food to mullahs at Ban Kado mosque in Ban Kado village of Rueso Ork sub-district.
The bomb, inside a cooking gas cylinder, was detonated by radio as the patrol led by Capt Sophon Klaocheed, commander of the 15131st company, passed by on a road in Ban Kado.
The explosion left a crater 90 centimetres wide and 60 centimetres deep.
Capt Sophon told police the attackers were hiding in a roadside rubber plantation. They detonated the bomb, but fortunately it did not explode completely, so his patrol survived.