Prime Minister Yingluck Shinawatra presided over a ceremony at the airport in a northern suburb of Bangkok. Airports of Thailand AOT.BK, which runs the country's main airports, said it expected 1.4 million passengers to use it this year.

Don Muang was temporarily the headquarters of the government's Flood Relief Operations Center and an evacuation centre for nearby residents before they were forced to move by rapidly rising water levels.

The domestic budget airlines that used Don Muang switched to Bangkok's main Suvarnabhumi airport, which was unaffected. One of them, Nok Air, said it would resume operations at Don Muang this week.

The Thai government spent 392 million baht on restoring the airport and Thailand's tourism authority contributed 1.2 billion.

Central areas of the capital escaped the flooding but more than 800 people died around the country over several months from late July.

(Reporting by Amy Sawitta Lefevre; Editing by Alan Raybould)

• A Permanent Economic Emergency