BANGKOK - FRUSTRATED tourists stranded by the anti-government occupation of Bangkok's main airports began trickling out of Thailand on Friday from a Vietnam War-era naval base, an official said.

Thousands of tourists have been trapped in the self-proclaimed 'Land of Smiles' since Tuesday, when protesters besieged the main Suvarnabhumi international airport and forced the suspension of all flights.

On Thursday, Thai aviation authorities gave airlines approval to use the one-runway U-Tapao naval base about 190 kilometres south-east of Bangkok and several planes have already landed.

'Around 40 flights are going to fly in and out of U-Tapao today,' said an official at the Department of Civil Aviation.

'Yesterday there were only half that number, around 20 flights, because most airlines did not know that U-Tapao has been opened.' He said most of the airlines which had requested permission to fly from the airport were Asian and Middle Eastern carriers.

Government officials have so far been unable to say how many tourists have left through U-Tapao, or how they will evacuate the tens of thousands of passengers believed to have missed flights because of this week's siege.

The Ministry of Tourism called a crisis meeting on Friday attended by airport officials and representatives from 50 airlines to try and map out a strategy for getting people in and out of the kingdom.

The runway at U-Tapao - used as a base for US troops during the Vietnam War - can handle all aircraft types, an official said, but has a small terminal and limited immigration and baggage capacity.

It is near the resort city of Pattaya.

Carriers which confirmed on Friday that they would send flights to U-Tapao included Malaysia Airlines, Singapore-based Jetstar Asia, EVA Airways of Taiwan, and Malaysia-based low-cost carrier AirAsia.

South Korean carriers sent special flights Thursday to bring out passengers from U-Tapao, and more were to leave Friday.

Thai Airways has made 'ad hoc diversions' into U-Tapao but its operation is otherwise severely affected, said Andrew Herdman, director general of the Association of Asia Pacific Airlines.

'It's fair to say the operation is crippled,' he said.

Some carriers said they were trying to accommodate passengers at other Thai destinations they served.

A spokesman for China Airlines in Taiwan said: 'We are increasing Taipei-Chiang Mai flights to carry Taiwanese passengers back home as many of them are moving from Bangkok to Chiang Mai for exit.'

AirAsia and Silk Air, the regional wing of Singapore Airlines, also fly to Chiang Mai, where Thai premier Somchai Wongsawat was himself forced to divert to when he returned home from a foreign trip on Wednesday.

Mr Stephen Forshaw, a Singapore Airlines spokesman, said on 938Live radio that if seats were available on Silk Air they would try to accommodate passengers affected by the Bangkok shutdown.

'We're looking at creative and reasonable ways to get people moving again,' he said.

Australia's major airline Qantas has diverted all flights to and from the Thai capital to Singapore since Tuesday.

Foreign Minister Stephen Smith told the Australian Broadcasting Corporation his government was exploring every option 'to do our best to look at all the contingencies for getting Australians out of Bangkok'. He did not elaborate.

All Nippon Airways and Japan Airlines said they were considering special flights to bring home stranded passengers.

Protesters trying to topple the elected government have vowed to stay at Suvarnabhumi until the prime minister resigns.

On Thursday, the smaller Don Mueang airport, which serves domestic routes, was also forced to shut its doors when protesters surrounded it, cutting almost all air travel in and out of Bangkok.

The government-run Tourism Council of Thailand has said the kingdom was losing about US$7 million (S$10.5 million) a day in tourist revenue during the airport closure - a huge blow to the vital industry.

In the current high season, up to 70,000 passengers should be arriving at Suvarnabhumi every day. -- AFP