Violent clashes between Thai and Cambodian soldiers erupted again on the border on Sunday evening, despite both countries agreed a ceasefire yesterday.
Reports said the fighting extended over 10 kilometres, from Phum Srol village to Phu Makhua Rung village in Si Sa Ket's Kantharalak district.
There were heavy artillery exchanges, leaving many villagers injured.
Army spokesman Sansern Kaewkamnerd said the clashes broke out after bullets were fired from the Cambodian side and Thai soldiers had to fire back.
The gunfire exchanges had not yet ended, Col Sansern said.
He said high ranking military officers of the Army Region 2 were holding talks with Cambodian army commanders in the region to find ways to stop the border fighting as soon as possible.