Thaksin phones in to Pheu Thai campaign rally in Si Sa Ket

"The weather in Dubai is very hot, soaring to 51 degrees [Celsius] and, with your help to carry me back, I want to return to Thailand," he said in his telephone message to about 500 supporters.

He said the by-election victory last week in Sakon Nakhon was tantamount to transporting him to the borders and that votes for Pheu Thai candidate Surachart Chanpradit in Si Sa Ket would assist him in re-entering Thailand.

His call, which lasted about five minutes, was seen as a last-ditch attempt to sway sentiment in favour of the main opposition party in its race against the coalition Chart Thai Pattana Party.

In regard to tomorrow's rally by the red shirts at Sanam Luang, Prime Minister Abhisit Vejjajiva told reporters in Beijing that his government had no objection to a peaceful demonstration.

Authorities are obligated to enforce the law, however, if the crowds turn unruly, he said.

Abhisit reminded his opponents that the world community was keeping a close watch on the situation in Thailand and that fellow Thais should not try to achieve certain vested interests regardless of the turmoil caused, at a time when foreign friends had been rallying behind the efforts to restore normalcy.

Democrat Party spokesman Buranaj Smutharaks said the main coalition party would monitor the red-shirt rally around the clock.

Buranaj voiced concern about the situation spiralling out of control because rally organisers and Thaksin often relied on fiery rhetoric, speaking for instance of elevating the struggle into a civil war, in order to incite crowds.

He said the red shirts wanted their rally, which coincided with the prime minister's visit to China, to embarrass the government.

Metropolitan Police commissioner Lt-General Worapong Chewpreecha ordered all police officers in the capital to report for duty for the duration of the red-shirt rally. No sick or personal leave will be granted, he said.

He also reminded the red shirts to confine themselves to their rally site at Sanam Luang, saying police would not allow a march or a blockade at Government House.