Junta defectors said Light Infantry Battalion 102 disobeyed orders to advance during fierce fighting with resistance forces in Karen State.
Junta forces have conducted multiple artillery strikes day and night since Monday near the Thai border.
As regime losses mount, the Karen National Union said that the combat ability and will to win of junta forces has declined dramatically.
The Cobra Column says large numbers of regime troops were routed on the strategically important Myawaddy-Waw Lay road.
Resistance groups and regime forces are engaged in a fierce battle near the strategic Ukayit Hta military outpost in southeast Myanmar.
The Cobra Column says it killed at least eight soldiers near the Thai border who were trying to reach troops injured earlier in the week.
They were among a unit of regime troops that was decimated by Cobra Column on the road leading to a strategic outpost in Karen State, the group said.
The Cobra Column resistance group said it found five dead soldiers, including a captain, after a clash on the road to the military’s Ukayit Hta outpost in Karen State.