BANGKOK – Hundreds of red-shirt supporters of former Prime Minister Thaksin Shinawatra rallied Friday, aiming to win more than a million signatures for a petition seeking a royal pardon for the fugitive leader.

The rally at Sanam Luang, a public square near Bangkok's Grand Palace, is expected to draw a crowd of 30,000 in a show of support for the exiled billionaire, who was sentenced in absentia last October to two years in prison for graft.

He has faced injustice by undemocratic means. Bringing him back would make Thailand a real democratic country, said Jatuporn Prompan, a core leader of the United Front for Democracy against Dictatorship (UDD).

The petition calls on 81-year-old King Bhumibol Adulyadej, who is considered semi-divine in Thailand, to pardon Thaksin and allow him to return home a free man after almost three years in globe-trotting exile.

The campaign has caused outrage among royalists and political opponents, who accuse Thaksin of trying to drag the revered monarch into his personal disputes.

Bhumibol, who is the world's longest-reigning monarch, is officially above politics but has previously intervened during times of crisis.

The signature collection ends at midnight Friday (1700 GMT). The UDD said it would take about a week to verify the signatures before submitting the petition to the king.

Analysts say the campaign is an attempt to show Thaksin's popularity has not waned since his removal in a 2006 coup and his subsequent graft conviction.

(For a Q+A on Thaksin's political strategy, click IDn:BKK194290])

Critics say it is unlikely the UDD will actually submit the petition because of the implications of involving the monarchy in politics. Acts deemed offensive to the institution are punishable by up to 15 years in prison in Thailand.

The extra-parliamentary UDD resumed its anti-government protests last month in its biggest rally since violent street clashes that forced Prime Minister Abhisit Vejjajiva to impose a state of emergency in the capital in April.

An army crackdown on thousands of red shirts in April sparked Thailand's worst street violence in 15 years and severely dented investor confidence.

The UDD says Abhisit is an illegitimate stooge who came to power because of parliamentary defections -- including some by Thaksin allies -- it says were engineered by Thailand's heavily politicized military.

(Reporting by Chalathip Thirasoonthrakul; Writing by Kittipong Soonprasert; Editing by Martin Petty and Sanjeev Miglani)

Thailand