He urged both sides to show restraint and negotiate a peaceful resolution.
Our Southeast Asia correspondent, Karen Percy, reports Bangkok is urging its people in Cambodia to return home.
Thailand has air force jets and cargo planes on standby ready to evacuate its citizens if the dispute escalates.
About 1,500 Thais live and work in Cambodia.
The two countries fired guns and rockets at each other on Wednesday along Cambodia’s northern border, which has been the subject of a land dispute for decades.
Two Cambodian soldiers were killed, and a number of Thai soldiers were injured in the clashes.
The Thais are worried about a repeat of events in 2003, when misconstrued comments by a Thai actor about the Angkor Wat temple site caused a violent backlash.
Thai businesses in Phnom Penh and the Thai embassy were attacked.
Both sides are moving more weapons into the border region, where local military leaders from both sides are expected to meet today to try to resolve the conflict.