Thai troops did not use cluster munitions during the clashes with Cambodian troops, as claimed by Cambodian leader Hun Sen, army spokesman Sansern Kaewkamnerd said on Thursday.
Col Sansern then accused the Cambodian army of using cluster munitions against Thailand.
Sgt Thanakorn Poonperm sustained shrapnel injuries to his head and later died in hospital. The shrapnel was from a cluster bomb, the spokesman said.
The Cambodian army claimed that cluster munitions found along the disputed border area were fired from the Thai side.
Amnesty International earlier said firing cluster munitions into residential areas is a violation of international human rights standards.