BANGKOK, Nov 15, 2009 (AFP) - Thousands of demonstrators from Thailand's royalist "Yellow Shirt" movement protested in Bangkok Sunday against a visit to Cambodia by their arch-foe, fugitive former premier Thaksin Shinawatra.
The group said it had called the rally to express outrage at the neighbouring country's appointment of Thaksin as an economic adviser and Phnom Penh's refusal to extradite him during his four-day trip there this week.
The yellow-clad People's Alliance for Democracy (PAD) led mass protests against Thaksin before he was toppled in a 2006 coup, and blockaded Bangkok's airports in late 2008 to force Thaksin's allies out of government.
Police estimated that around 4,000 people had gathered by the official start of Sunday's rally at at 4:00 pm (0900 GMT) at a parade ground in downtown Bangkok, but said that more were expected to arrive later.
"Our duty is to protect and preserve the country's honour and dignity and the monarchy. Cambodia violated the extradition treaty and allowed a convicted person to be its adviser," senior PAD leader Somsak Kosaisuk told AFP.
"This action harms our country's prestige. We will denounce both convicted Thaksin and (Cambodian Prime Minister) Hun Sen at the protest," Somsak said.
Thaksin left Cambodia on Saturday for Dubai, where he has spent most of the time since fleeing Thailand in August 2008 to avoid a two-year jail term for corruption. Thailand has also frozen 2.2 billion dollars of his assets.
The nationalist PAD said it was also gathering to express outrage at comments that billionaire Thaksin made in a newspaper interview in which he called for reform of institutions around Thailand's revered monarchy.
The issue is sensitive because 81-year-old King Bhumibol Adulyadej -- a major force for stability in the politically divided nation -- has been in hospital for the past two months.
Deputy national police spokesman Piya Utayo said around 1,500 police officers were deployed for the rally.
Thaksin's visit to Cambodia sparked a diplomatic crisis between Bangkok and Phnom Penh, with relations already tense after a series of deadly clashes in the past year over a disputed temple on their border.
The neighbours recalled their respective ambassadors and expelled the first secretaries of each other's embassies. Cambodian police have also charged a Thai man with spying for the Thai embassy.
The coalition government of Thai Prime Minister Abhisit Vejjajiva -- which took power soon after the Yellow Shirt airport blockade -- has been rattled by the prospect of Thaksin using Cambodia as a base for a political comeback.
Thaksin, a telecommunications mogul, remains hugely influential in Thailand's political scene, which remains bitterly split between largely anti-Thaksin urbanites and his die-hard backers among the rural poor.
His so-called "Red Shirt" supporters have themselves staged several massive protests over the past year, including the disruption of a summit of Asian leaders and subsequent riots in April.
But analysts said that by siding with Cambodia he could lose public support.
"To identify yourself with Hun Sen is a terrible political mistake," said Bangkok-based political analyst Chris Baker, who has written a biography of Thaksin.
"I think Thaksin has considerably weakened his own position. He's in a desperate state to try to negotiate over his money and he's overplayed his hand very badly indeed."
In September, Yellow Shirts calling for the Thai government to defend the country's sovereignty clashed with police and Thai villagers during a protest close to the Preah Vihear temple, leaving dozens of people injured.