Thaksin Shinawatra's supporters defended his controversial letters to Asean and US leaders as unremarkable but critics were out in force saying he had embarrassed himself and the nation.

A former Thai ambassador to several Western and Asian countries said Thaksin compromised the Kingdom's sovereignty when he wrote the official letters in April and June.

The letters, sent to Asean leaders in April and to US President Bush in June, were inappropriate, said the diplomat, who asked to remain unnamed.

"The contents suggest that our leader has effectively taken domestic political issues into the international arena. It's unprecedented because we've long prided ourselves on being a sovereign nation, since the reign of King Ramkhamhaeng the Great.

"As far as I'm aware, there has never been a Thai leader who did such a thing," said the former ambassador. The source said no official letters should have been sent to world leaders while the premier only held caretaker status.

"If the matters were critical, then Thaksin should have met with the ambassadors of these nations.

"In addition, Thaksin should not have tried to define democracy in the letters and then attacked his political opponents with bias. Poll boycotts and street demonstrations are part of a democratic system," the diplomat said.

Anti-Thaksin messages on political websites note that Thaksin has in the past condemned American influence in other nations' domestic affairs, and criticised his switch to a "cry baby" attitude.

Some political academics accused Thaksin of "washing his dirty linen internationally".

Sangsit Piriyarangsan, director of Chandrakasem Rajabhat University's Good Governance Research Centre, said Thaksin acted inappropriately by portraying his opponents as undemocratic and a threat to the political system.

"He thinks he is the only defender of democracy and he must assume the US president will agree," said Sangsit.

The troubled premier might even be trying to bolster international support in case he uses force to regain power, the academic suggested.

"Thaksin does everything for himself. The letter is like selling off our country to foreigners," said Sangsit.

Political observer Prayad Hongthongkham said by giving Bush distorted information on the political situation, Thaksin was acting as if the Kingdom was a US colony.

"He's obviously feeling insecure," Prayad said.

Surat Horachaikul, another Chulalongkorn University political scientist, said Thaksin had the right to explain the country's situation to world leaders but it should be done in an objective fashion.

"The letter was an attempt to seek allies for himself. It does not benefit the country as a whole," Surat said.

Panitan Wattayakorn, also of Chulalongkorn, argued Thaksin's actions could be seen as an attempt to seek Washington's intervention.

"The letter concerns only Thaksin's political interests," Panitan said.

Former foreign minister Surin Pitsuwan said the letter contradicted Thaksin's claim to be a defender of democracy. "It is hypocritical," Surin said. "It was a one-sided explanation meant only for his political gain."