'At the moment the army is interfering... Those people who interfere in forming the government must stop and withdraw,' Thaksin said in the 20-minute video, though a live phone-in scheduled to follow was cancelled at the last minute.

Police said 50,000 supporters of Thaksin - who is living in exile to avoid corruption charges at home - had gathered in red shirts to show their allegiance, two days before a crucial vote by lawmakers for a new premier.

Prime minister Somchai Wongsawat, Thaksin's brother-in-law, was forced from office in a court ruling on December 3 that splintered the ruling coalition.

Thaksin, who was ousted in a 2006 coup but still enjoys wide support among poor, rural Thais, accused the army and judicial system of meddling after coalition members defected last week to support the opposition Democrat Party.

'We are still under a military coup... They have used the court to crack down on politicians. There is no other place in the world where a party has been dissolved twice,' he said, referring to the banning of his political party Thai Rak Thai and its successor People Power Party.

'They must respect the people's decision... They should behave with a sportsman's spirit and not interfere,' he added.

Rally leader Veera Musikapong said a live phone-in to Bangkok's National Stadium had been cancelled in the hope of securing support for a new governing coalition led by Puea Thai, the party newly formed to regroup Thaksin's allies.

Two former coalition members had promised to back Puea Thai if the telephone address was cancelled, he said.

'I will not conduct the phone-in but we will be the core party in a national coalition. Don't betray us otherwise you will meet with red shirts all over the country,' Mr Veera warned.

Meanwhile Thaksin issued a warning to those lawmakers who had defected to support the opposition Democrat Party.

'People know they will be punished,' Thaksin said.

For most of the day, the crowd cheered and danced as speaker after speaker criticised efforts by the Democrat Party to form a new government as early as Monday and accused the army of pressuring the courts to force the ruling coalition from power.

The event is seen as a last-ditch effort by Thaksin and his followers to rally support ahead of Monday's parliamentary session to elect Thailand's new leader.

Previous Prime Minister Somchai Wongsawat was forced to step down earlier this month, when a court dissolved the pro-Thaksin People's Power Party for fraud committed in the December 2007 election that brought it to power.

Two rival parties claim they have enough support to form a government and select the country's next leader, and intensive behind-the-scenes maneuvering has been taking place to woo legislators not tied to either side.

Thailand's Democrat Party - which has been in opposition to the Thaksin camp since 2001 - says it has enlisted enough lawmakers from other parties to form a parliamentary majority and name its leader, Abhisit Vejjajiva, the prime minister.

Party spokesman Buranaj Smutharaks expressed confidence that Oxford-educated Abhisit would emerge as the country's leader. He said Thaksin made daily calls over the past week to former supporters who had defected to the Democrats but was unable to persuade them to return.

Thaksin is expected to rally support for the Phuea Thai party, comprising most politicians from the disbanded People's Power Party and its predecessor, the Thai Rak Thai party, Thaksin's ruling party from 2001 until he was ousted by a 2006 military coup after being accused of corruption and abuse of power.

Phuea Thai members claimed on Friday they had enough backing in Parliament to elect former national Police Chief Pracha Promnok, leader of the allied Puea Pandin party, as prime minister.

The new leader will be Thailand's fifth prime minister in a little more than two years. The country has been disrupted by months of protests by an anti-Thaksin alliance that occupied the prime minister's office from late August until last week.

The alliance last week also abandoned its week-long occupation of Bangkok's two airports - which stranded upward of 300,000 travelers - after Mr Somchai, who is Thaksin's brother-in-law, was forced out of office.

The protest alliance has also injected itself into the battle for the premier's job, on Friday threatening new action if Parliament elects a new prime minister that it finds unacceptable.

It said it 'opposes any proxy prime minister from the Phuea Thai Party and any prime minister from a political party that is part of a coalition involving the Phuea Thai Party, which is a newly established proxy political party of the Thaksin regime'.

Thaksin fled Thailand in August. In October, a Thai court sentenced him absentia to two years in prison on conflict of interest charges.

Thaksin will talk about 'the powers behind the coup that ousted him and the people who tried to make him out to be a villain, and about the events that have led to the current crisis,' said Nattawut Sai-kua, a rally organiser.

Thaksin told his supporters at a Nov 1 rally that he had been persecuted by his political enemies, and that there was nothing that could allow him to return 'except for the king's mercy or the power of the people'.

Thaksin, a former telecommunications magnate, is still supported by many in the impoverished countryside because of his populist policies while in power. -- AP, AFP