Thailand threatened yesterday to extradite its former leader, Thaksin Shinawatra, if he takes up an offer of refuge from its neighbour and rival, Cambodia.

The Thai Prime Minister, Abhisit Vejjajiva, made the threat after his Cambodian counterpart, Hun Sen, offered his house to Mr Thaksin, who was deposed as prime minister in a 2006 military coup and convicted of corruption in absentia last year. The invitation appears designed to embarrass Mr Abhisit, who will today welcome Asian leaders, including Mr Hun Sen, to a regional summit in a Thai beach resort.

“Once Thaksin enters Cambodia the extradition process will begin,” Mr Abhisit said. “I have talked with Hun Sen several times and he’s told me that he’s Thaksin’s friend but that he will separate friendship from duty and international affairs.”

The diplomatic spat unites two conflicts which have dogged Thai politics for the past few years — the struggle between supporters and opponents of Mr Thaksin, and the ill feeling between Thailand and Cambodia.

Mr Thaksin was the most popular, but also the most divisive, prime minister Thailand has ever known, adored by many poor rural Thais but loathed in equal measure, especially by the middle class. Since he was deposed by army generals, who restored democracy the following year, he has taken temporary refuge in China, Britain and Hong Kong, before settling most recently in Dubai.

Meanwhile Thailand has been divided by violent confrontations between his red-shirted supporters and opposing “Yellow Shirts”. When Mr Abhisit hosted an international summit in April he was humiliated when Red Shirt demonstrators burst into the venue, forcing the assembled leaders to evacuate on helicopters.

About 36,000 police and soldiers have been assembled to prevent anything similar disrupting today’s meeting of the Association of Southeast Asian Nations in the town of Cha-am.

It is unclear whether Mr Thaksin will take up Mr Hun Sen’s offer, which may be intended as much as an expression of contempt for the current prime minister as a helping hand to his predecessor.

Mr Thaksin’s government provided loans for aid projects in Cambodia and helped with the upgrading of a road. Since last year relations have become acrimonious with the revival of a territorial dispute about the mountaintop Preah Vihear temple on the border.

Preah Vihear can be reached more easily from Thailand than Cambodia but the territory was awarded to Cambodia in 1962 by the International Court of Justice, after legal arguments about maps of produced during Cambodia’s French colonial period.

This month Mr Hun Sen ordered troops to shoot anyone illegally crossing into Cambodia. T Despite the extradition threat, Mr Abhisit may be happy to leave Mr Thaksin in exile for the time being. His arrest and imprisonment would stir up the rage of his supporters at a time of anxiety for Thais, whose beloved king, Bhumibol, is in hospital with apparent pneumonia. The Stock Exchange of Thailand sank sharply last week after rumours, denied by his doctors, that he was dying.

“It is a liberty of a prime minister of a country to have as many friends as he wishes,” the Thai deputy prime minister, Suthep Thaugsuban, said yesterday regarding Mr Hun Sen’s invitation.

“If he is a friend of someone whom we have a problem with, there is no reason for us to be mad at the entire country. What he [Hun Sen] said and felt may be different from what many of us here do . . . If we feel that he has been misinformed, we should provide him the correct information.”

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