AFP

Thai Prime Minister Abhisit Vejjajiva insists he will go ahead with a trip to Australia next week even though the visit coincides with mass anti-government rallies at home.

Supporters of deposed premier Thaksin Shinawatra, known as "Red Shirts" because of their usual garb, are gathering in Bangkok on March 14 after a court ordered the seizure of most of Thaksin's fortune worth $US2.3 billion ($A2.55 billion).

Abhisit said he would carry on as planned with his March 13-17 trip to Australia despite the rallies, adding that he would assign Deputy Prime Minister Suthep Thaugsuban to oversee events at home.

"But I will closely monitor the situation," Abhisit said.

The military stepped in to oust Thaksin while he was out of the country attending the UN General Assembly in New York in September 2006.

Abhisit, who came to power in December 2008 after a court ruling drove Thaksin's allies from government, said authorities may still declare harsh security laws to deal with the protests.

Thailand's pro- and anti-Thaksin camps have both conducted destabilising street campaigns since the tycoon was ousted, with some of the demonstrations turning violent.

The Red Shirts say they expect up to 600,000 people to attend this month's rallies, with people starting to gather from around the country on March 12 before the main demonstration two days later.

Suthep, who is also in charge of national security, ruled out holding talks with Thaksin in a bid to halt the rallies.

"It's difficult to talk with him as he is completely angry," Suthep told reporters.

"I think it's not appropriate (to hold talks) as they are putting the country and its future at risk for one person."

He said soldiers and police would man checkpoints in every province next week to search vehicles heading to Bangkok for weapons and to check that protesters were carrying Thai identification cards.

"Migrant workers have no right to participate, even as onlookers," he said, referring to an estimated three million workers mainly from Burma, Cambodia and Laos, on whom the government is tightening restrictions.

Suthep also warned Buddhist monks not to take part in the rally, after the Red Shirts said that up to 20,000 saffron-robed monks would join in.

Red Shirt riots in April derailed a major Asian summit and left two people dead.