
Cambodian PM Hun Sen, Indonesian President Susilo Bambang Yudhoyono, Malaysian Prime Minister Najib Abdul Razak and Philippine President Gloria Macapagal Arroyo will be absent.
The opening ceremony will be held at 9.45am.
Hun Sen will arrive in Hua Hin at 4pm, as he is busy with an official visit from South Korean President Lee Myung-bak.
Asean Secretary-General Surin Pitsuwan confirmed that Hun Sen needed to welcome the South Korean leader and he would rush to the summit immediately after the visit.
Hun Sen will definitely attend the summit and his delay has nothing to do with the ongoing border dispute with Thailand, Surin said.
Yudhoyono will be delayed by his inauguration for a second term as president and will arrive in Thailand at 8.30pm.
Najib, meanwhile, has to attend a parliamentary budget debate and will arrive around the same time as Arroyo, at about 9pm.
It is very rare for Asean to have so many leaders absent at the opening ceremony of a summit. Asean ministers met yesterday to finalise the summit agenda and documents for their leaders.
Cambodia's Foreign Minister Hor Namhong and Indonesia's incoming foreign minister, Raden Mohammad Marty Muliana Natalegawa, did not however attend the meetings. The former needed to accompany Hun Sen, while the latter has not yet been sworn in.
However, the remaining ministers were able to continue the meeting to prepare the agenda and documents for the summit, according to Foreign Minister Kasit Piromya, who chaired several ministerial meetings yesterday.
Asean leaders will discuss the issues of food and energy security, the global crisis and climate change. During the summit, as many as 43 documents will be noted, signed or adopted by leaders and ministers, Kasit said.
The key documents include the declaration of the inauguration of the Asean Intergovernmental Commission on Human Rights, the declaration on the Strengthening of Asean Education Cooperation, and the Asean leaders' statement on Asean connectivity. -