
The other three are still undergoing treatment in hospital. Boonrit suffered a severe shrapnel injury to the left side of his head.
He remained unconscious after undergoing an operation on Wednesday and is now on a respirator in the intensive care unit.
"He is unresponsive and has cerebral oedema," Chalerm said. The public health minister has assigned two specialists - Dr Monchai Viwattanasittipong, an accident expert, and Dr Prawatwong Wongsrikawe, a neurosurgeon - to look after Boonrit.
The three other hospitalised soldiers are undergoing treatment in Kantharalak district hospital in Si Sa Ket for minor injuries. They are SgtMajor Nattaphon, who suffered a bad sprain; SgtMajor Preecha Pokphan, who has a shrapnel wound on his right thumb; and Ranger Krissanarak Chandang, who suffered shrapnel to his right knee.
Doctors removed the shrapnel from Preecha and Krissanarak, and they will be released from hospital tomorrow, said Chalerm.
Wednesday's clash over a disputed area on the Cambodian border injured 10 Thai soldiers.