Prime Minister Samak Sundaravej will dispatch a special envoy to Burma today to attempt to convince the junta leaders to permit foreign relief teams, notably those from the United States and the United Kingdom, to help those hit by Cyclone Nargis.
The US and UK ambassadors to Thailand have asked the premier to assist.
Samak said earlier that he had contacted Burmese generals in the capital of Naypyitaw and would fly to see them tomorrow, but subsequent talks suggested that the junta's leaders were "too busy" to welcome the Thai leader.
Lt-General Niphat Thonglek, director of the Supreme Command's Boundary Affairs Department, and Thai Ambassador to Burma Bansarn Bunnag will instead carry a letter from Samak to Burma's Prime Minister Thein Sein.
The letter conveys condolence messages and concerns from Thai leaders to Burmese leaders and people, Niphat said. However, he declined to reveal further details, such as whether the letter also asked for permission from the junta for Western relief teams to enter the country.
The British ambassador to Thailand, Quinton Quayle, met Samak yesterday to discuss the possibility that Thailand could use its influence to convince Burmese leaders to open the country to Western assistance.
"In order for the international community to assist the Burmese people at this time of pressing need, the Burmese government should provide immediate visas to allow rapid access for specialists and aid to reach those affected as soon as possible," Quayle said.
The UK through its Department for International Development has made an initial pledge of up to £5 million (Bt311 million) - the largest single contribution by any one country so far - to go to United Nations, Red Cross and NGO partners on the ground to help meet immediate needs.
The Burmese junta asked for humanitarian assistance to help millions of affected people after Cyclone Nargis hit the country last week, but has refused to grant visas for foreign relief teams.
US Ambassador to Thailand Eric John met Samak on Thursday to ask the premier to help facilitate Burmese visas for the US teams who are now waiting in Bangkok.
More than 65,000 people are dead or missing in the region, with fears the death toll will top 100,000. More than 1 million people have been left homeless.
The UN has blasted the military government, saying its refusal to let in foreign aid workers to help victims of a devastating cyclone was "unprecedented" in the history of humanitarian work.
The UN's World Food Programme, however, said it was able to begin delivery of food and plastic tarpaulins to cyclone-devastated areas in the Irrawaddy delta.