Demonstrators opposed to the previous government's ties to ousted former premier Thaksin Shinawatra occupied the capital's international and domestic airports for more than a week from late November to early December.

The protesters from the royalist People's Alliance for Democracy movement dispersed after a court verdict brought down the government, but a Bank of Thailand study said the economic damage from the siege was huge.

"The political unrest has not only affected the tourism industry but also other related industries," said the study, titled Thailand's Tourism Industry After The Closure Of Airports.

"Based on analysis, total losses were 290 billion baht, equivalent to 3.0 of nominal GDP (gross domestic product)," the study added.

It said the losses included 120 billion baht in the service industry, 90 billion baht in logistics and 60 billion baht in industry.

The shutdown of Suvarnabhumi and Don Mueang airports between November 25 and December 4 prevented 3.4 million tourists from visiting Thailand.

"The losses are more serious than SARS and the tsunami because those two were short-term," the study said, referring to the global Severe Acute Respiratory Syndrome outbreak in 2003 and the deadly 2004 Indian Ocean tsunami.

The study predicted that tourist arrivals in Thailand this year would fall 8.8 per cent year on year to 12.8 million.

Thailand's tourism industry accounts for 5 per cent of GDP and employs some 2 million people or up to 7 per cent of the country's total workforce.

The losses from the airport blockade have added to the economic challenges that Thailand faces as a result of the global financial crisis, with the export-dependent kingdom's trading partners struggling.

New Prime Minister Abhisit Vejjajiva, a Thaksin foe who came to power in December 15 after the dissolution of the previous government, has promised a 300 billion baht economic stimulus plan.

But he warned in an interview in December that tackling Thailand's current economic woes would be a "tougher job" than dealing with the 1997 Asian financial crisis.