BANGKOK - THAILAND is offering its naval airbase on the eastern seaboard as an alternative for airlines after its two Bangkok airports were closed by anti-government protests, a top aviation official said on Thursday.

Aviation Department chief Chaisak Angkasuwan said he was ready to let airlines use U-Tapao, a small airport already used for some short domestic routes and international charter flights, 140 kilometres south-east of Bangkok.

'If any airline wishes to land or take off from U-Tapao, send us a request and we will immediately grant it,' he said.

'We are doing this to help passengers who wish to go home,' he added.

A blockade by anti-government protesters at Bangkok's Suvarnabhumi airport, a major Asian air hub, entered its third day on Thursday, causing the cancellation of all flights and stranding thousands of tourists in the Thai capital.

Members of the People's Alliance for Democracy (PAD) also laid siege to the old Don Muang airport, shutting the domestic hub and effectively severing air links to the city of 8 million people.

U-Tapao, a front-line base for the US Air Force during the Vietnam War, has one runway.

National carrier Thai Airways , which operates 140 flights a day to and from Suvarnabhumi international airport, said on Thursday it was considering using U-Tapao.

Suvarnabhumi international airport has been seized by protestors since Tuesday night. With baggage trolleys converted into noodle stalls and check-in desks used as beds, all the signs at Suvarnabhumi airport are that protesters are in for the long haul.

Enterprising vendors have even moved in to sell the plastic hand-shaped clappers that have become the bizarre signature of Thailand's anti-government movement.

Built to wow the world and opened to much fanfare in September 2006, the new terminal is now overflowing with demonstrators who have taken a liking to the high-tech facilities.

'It is very convenient - we have clean toilets,' said 46-year-old businesswoman Chaleepun Parama.

Cleaning staff came in on Thursday to make sure that every aspect of the three-billion-dollar glass-and-steel structure, the third largest airport building in the world, is kept fresh.

Pranee Lampen, 52, said she was very pleased with the sleeping arrangements, which she preferred to another protest camp at the prime minister's occupied Government House offices.

'We don't have to build a place to sleep, we just use a mat and we can sleep,' she told AFP. 'My only complaint is that the air conditioning is too cold during the night.'

Thousands of supporters of the People's Alliance for Democracy (PAD) marched on the key Southeast Asian transport hub on Tuesday and forced its closure as they upped their campaign to topple the democratically elected government.

They mostly rallied outside, but as airport authorities began evacuating about 3,000 stranded tourists on Wednesday, the supporters - draped in yellow to show allegiance to the monarchy - started trickling in.

After spending the night sleeping on floor mats, chairs and by check-in desks, they had by Thursday morning dug in.

'We have fought for six months. We have almost reached our goal. We will stay here,' said Chaleepun, who had accessorised her grey shirt with yellow arm bands.

PAD protesters also shut down Bangkok's smaller Don Mueang airport on Thursday, despite calls by the powerful army chief Anupong Paojinda that they disperse.

Prime Minister Somchai Wongsawat also refused Anupong's request on Wednesday that he dissolve the house and call new elections to solve the turmoil.

'If he (Somchai) stays, we stay,' said Chaleepun.

Demonstrators made sure that every need was catered for.

Pichsine Kitpakornsanti, who quit her job as a teacher to join the PAD protests, converted five baggage trolleys into food stores, giving out energy drinks, coffee and snacks.

'Those who are hungry, come my way!' she cried as protesters huddled around her wares. 'This is all for free - your payment is one smile.'

A delivery of 500 burgers were also on their way, she said.

Outside the cavernous departures hall, vendors sold headbands in the colours of the national flag and the clappers that have become a favourite of PAD loyalists.

They were put to vigorous use as protest coordinator Chaiwat Sinsuwong took to a makeshift stage and urged more supporters to join them at the airport - although they almost drowned him out.

The departures board was covered with banners calling Mr Somchai a 'tyrant', while others were more conciliatory, telling tourists 'If we have caused you any inconvenience, we sincerely apologise.'

A trickle of holidaymakers continued to show up.

'We just woke up today and we came to the airport. We were surprised that there were many people here,' said Mariuse Wisuiewski from Poland.

'We just learnt now that the airport is closed and there are no flights,' he said, before being herded away by an airport official. -- AFP