Bangkok - Thailand's 81-year-old King Bhumibol Adulyadej on Tuesday congratulated Barrack Obama on his inauguration as the 44th president of the US and sent his wishes for greater "progress and prosperity" for the American people.

"I am pleased to extend to Your Excellency my sincere congratulations and best wishes for your success and happiness as well as for the greater progress and prosperity of the United States of America and her people," said the king in a congratulatory message to president-elect Obama.

Under Thailand's constitutional monarchy, the king is head of state, making him the appropriate government figure to congratulate the US president, who is also head of state.

Thai Prime Minister Abhisit Vejjajiva was also planning to send Obama a separate note of congratulations.

Thailand and the US have a long history of close diplomatic relations.

Thai King Mongkut, King Bhumibol's ancestor, famously offered US President Abraham Lincoln Thai elephants to assist him in the civil war. (dpa)