The leader of the opposition Democrat Party, Banyat Bantadtan, congratulated Prime Minister Thaksin Shinawatra on his victory shortly after polls closed.
Deputy party leader Abhisit Vejjajiva told reporters that the size of the victory would allow Mr. Thaksin's party to govern without coalition partners.
Mr. Abhisit says the win projected by the exit polls is about what he expected but adds he will wait to see the outcome of the official tally.
Mr. Thaksin subsequently thanked voters for their overwhelming support.
Mr. Thaksin says he thinks he has enough votes to set up a one-party government but adds a great deal of hard work remains.
Thai voters turned out in large numbers Sunday to deliver their verdict on the populist first term of Prime Minister Thaksin and his Thai Rak Thai Party.
In the working-class district of Klong Toey in central Bangkok, driver Mongkol expressed satisfaction with Mr. Thaksin's policies.
Mr. Mongkol said the government has done a lot of good for the poor.
Fifty-five year-old schoolteacher Supasri, says the most important thing for her is good governance.
"Reduce the corruption. Corruption is a major problem," she said.
She added that the economy, especially job creation, is also a major priority.
But civic groups say the economic policies are unsustainable and worry about civil liberties.
Chulalongkorn University Professor Kalaya says she is worried that the Thaksin government is rolling back a decade of democratic advances in personal liberties.
"We have a new form of authoritarianism, I think. From a military dictatorship, we now have a new form of dictatorship," said Professor Kalaya.
She acknowledges that most people like a strong leader, but she believes there should be a better balance between the governing and opposition parties. Nevertheless, she says this is the will of the people in free elections and those who disagree will just have to work harder in the future.
Thailand's constitution says that more than 200 votes are needed censure the prime minister, although only 100 are needed to summon cabinet ministers. Early indications show that the second Thaksin government could rule without such challenges.
Official election results are due within 30 days.