Opposition leader Banyat Bantadtan conceded defeat less than 90 minutes after television networks projected Thaksin's resounding victory.

"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.

"Thai Rak Thai will have a single-party government," Banyat predicted.

Media-savvy Thaksin stayed out of the spotlight as his party acknowledged the exit polls and said the premier would wait for official returns to make a statement.

"The public has given us their overwhelming support," TRT deputy leader Sudarat Keyuraphan quoted Thaksin as saying.

The projected win, which would hand Thaksin an unprecedented second term, was far larger than the rosiest forecasts, which most recently had predicted that the billionaire telecom tycoon's party would win 349 seats.

The leading opposition Democrat Party was set to take 80 seats, Chart Thai 20 and the newly formed Mahachon party one seat, according to the projections.

Even if all the opposition parties grouped together, they would not have enough seats to censure Thanksin's government in parliament.

"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 said.

Thai television released the exit poll results moments after polls closed at 3:00 pm (0800 GMT), despite an official ban.

Voting ran smoothly across the kingdom's 400 constituencies during the seven hours of balloting.

The win easily exceeds Thaksin's goal of controlling 350 seats in the lower House of Representatives.

The premier said as he cast his ballot earlier in the day that such a win would "be better, because we have a strategy, we have a plan."

The Democrat Party had already conceded it could not defeat Thaksin and had asked voters only for enough seats to censure his government in parliament.

Banyat earlier complained that the incidence of vote buying had doubled from the last election.

"There was a huge vote-buying effort last night" in southern provinces, which are Democrat strongholds, Banyat told Thai television after voting in the southern town of Surat Thani.

Vote buying has a long tradition in Thailand -- a survey released Saturday said the average rate this year was 513 baht (13 dollars) per ballot. Officials had banned the use of mobile phone cameras in voting booths.

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 tsunami 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 steadily trickled into polls.

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

Thaksin's military crackdown on the Islamic insurgency, which has left more than 580 dead, has drawn sharp criticism.

The prospect of an even more powerful premier has raised alarm among groups such as Human Rights Watch, which considers Thailand "a country of high concern."

In a country where every previous elected government has fallen either to military coups or political squabbling, Thaksin's is the first to survive a full four-year term.

The mogul has largely delivered on his promises to revive Thailand's fortunes after the 1997 Asian financial crisis and has proved a popular leader.