There have been heavy cross-border artillery exchanges between Thai and Cambodian forces for a third consecutive day.
Since the latest flare-up of a long-running territorial dispute, 10 soldiers on both sides have been killed and dozens wounded.
Each side is blaming the other for firing first. The Cambodians have accused Thai troops of shelling civilian villages and using cluster bombs, which are widely banned.
The Thai prime minister used his weekly TV address to say his country had no intention of invading or attacking anyone. But he added: “We have a duty to fully protect our own sovereignty.”
The fighting is over two ancient Hindu temples and the land surrounding them. It is a dispute that has been raging since the French colonial power left Cambodia in the 1950s.
Thousands of civilians have been moved to safety on both sides of the border.
The UN secretary general Ban Ki-moon has called for “maximum restraint”.
The leader of the Association of South East Asian Nations has meetings planned with the foreign ministers of both countries.