Bolstered by a humming economy and widespread approval of his response to the December tsunami tragedy, Thaksin's projected win surpassed even his and his party's rosiest expectations.

With 399 of 500 seats, according to television exit polls, Thaksin will be able to form the first elected one-party government in Thailand's history, leaving parliament unable to censure him.

His rivals, and human rights groups, fear that concentration of power will fuel what they see as authoritarian tendencies, especially in his heavy-handed response to the Islamic insurgency in southern Thailand.

Thaksin credited his anti-poverty programs for his success.

"In the past four years, we have worked hard for them, and we care, that's probably the magic of the victory," he told reporters at his party headquarters.

"If it's really 399, as exit polls show, it's a bit more than we expected," a relaxed-looking Thaksin said in a televised interview afterwards.

Early returns were trickling in from around the country late Sunday, with final tallies expected mid-day Monday. But television networks defied a ban on exit polls and predicted the outcome moments after polls closed at 3:00 pm (0800 GMT).

Opposition leader Banyat Bantadtan conceded defeat less than 90 minutes later.

"I was shocked when I saw the exit polls, that Thai Rak Thai managed to win 399 (seats) and the Democrats won only 80, but we have to accept what the public gave us," he told reporters.

The returns shattered the Democrat Party, which lost ground and failed to even near its goal of 201 seats.

"If the actual results match the exit polls then we have to think about how to improve the party," Bangkok's Democrat deputy governor Samart Ratchapolisitte said.

Thaksin's current coalition partner Chart Thai won 20 seats, while the newly formed Mahachon party took just one, according to the projections.

Just ahead of midnight Sunday just nine constituencies -- all in Bangkok -- had reported returns with more than 50 percent of ballots counted. Several constituencies had yet to begin the count as all ballot boxes needed to be present in the counting station for the tally to begin.

The results appeared to give the billionaire telecom tycoon a sweeping mandate to push ahead with his proposals to overhaul the economy by stimulating the rural areas while encouraging exports and foreign investment.

"He will say this is a strong mandate to do whatever he wants, with more centralisation of power. Whether it's good for Thailand or not, it's difficult to say," said Prapat Thepchatree, director of the centre for international policy studies at Thammasat University.

"The tsunami has had a positive effect for Thai Rak Thai. I think psychologically the effect was substantial because it was confirmation in people's minds that he has been a good manager," he told AFP.

The kingdom's 44 million eligible voters cast their ballots six weeks after December's tsunami devastated six southern provinces, killing nearly 5,400 people.

In the hardest-hit province of Phang Nga, the army drove voters left homeless by the disaster from camps to ballot boxes. Substitute polling stations were found for two temples being used as makeshift morgues.

In the four southernmost provinces, where Thaksin has battled Islamic insurgents since January 2004, heavily armed forces patrolled the streets as voters cast their ballots.

No violence was reported in the region which has seen almost daily killings, police said.

Thaksin's enormous edge going into the polls did not eliminate the darker side of Thai politics.

A survey released Saturday found rampant vote-buying, with ballots going for an average rate of 513 baht (13 dollars) each. Officials had banned the use of mobile phone cameras in voting booths.

Alcohol sales were also banned for election day, leading to an absence of victory parties in the capital.