Thailand fears it will have to give up 4.6 sq km around the temple if it is listed on behalf of Cambodia only.
The royal birthday celebration for the king, who ascended to the throne in 2004 after the abdication of his father, Norodom Sihanouk, began yesterday and will continue until tomorrow.
The king traditionally conducts Buddhist rites at his palace in the capital, but had chosen to fly by helicopter to an area close to Preah Vihear temple, perched on the border, officials said.
Cambodia is also mulling the idea of introducing a national holiday on June 15 to mark the 1962 anniversary of the International Court in The Hague deciding that the temple, which is sacred to both Cambodians and Thais, lies within Cambodian territory.
Border demarcations, both around Preah Vihear and in disputed coastal waters, remain a sensitive issue for both nations.
Thai Foreign Minister Noppadon Pattama said on a radio programme yesterday that the Thai side has included the coastal border in negotiations about Preah Vihear with Cambodia. The dispute over the temple could be ended only if both countries reached agreement on the overlapping coastal territory first, he said.