Sutthisak Meansen, 44, had left home to go fishing near the bridge at Nam Khem village Moo 9 in tambon Ban Na, reports the Bangkok Post.
As he walked towards his chosen fishing spot, a bomb exploded under his foot. His right leg was blown off and he sustained other serious wounds to his right arm, police said.
Nearby residents rushed to help him and he was quickly taken on a motorcycle to Chana Hospital.
Police believed the bomb was planted by insurgents. It was 4-5 kilometres from the mosque where soldiers and armed insurgents clashed on Thursday morning. Three militants were killed as they tried to break through security forces surrounding the Koran study centre in tambon Ban Na of Chana district.
A bomb disposal team was sent to inspect the area, for fear more bombs might be buried on the path to the clash scene.