Thai prime minister Abhisit Vejjajiva conceded defeat in a national election today after exit polls showed the opposition Puea Thai Party winning a majority of parliament's 500 seats.
He congratulated Yingluck Shinawatra, Puea Thai's candidate for prime minister and sister of ousted premier Thaksin Shinawatra, on her victory.
"It is now clear from the election results so far that the Puea Thai Party has won the election, and the Democrat Party concedes defeat. I would like to congratulate the Puea Thai Party for the right to form a government," he said on television.
Ms Yingluckwa, a 44-year-old businesswoman and political novice, is now poised to become the country's first female prime minister.
"Mr Thaksin called me to congratulate me and encourage me," Ms Yingluck said of her brother, a billionaire ousted in a 2006 coup who now lives in Dubai to avoid jail for graft charges he says were politically motivated. "He told me that there is still much hard work ahead of us."
With nearly 50 per cent of total votes counted, Ms Yingluck's party had won just 249 of the 500 seats, according to the Election Commission.
Polling by Bangkok's Suan Dusit University, considered the most historically reliable, showed Puea Thai winning 313 seats with incumbent prime minister Abhisit Vejjajiva's Democrat Party taking just 152 - worse than the Democrats' last performance in 2007. Bangkok's Assumption University put the number of seats won by the opposition at 299 in its exit poll.
The results, if accurate, are a rebuke for Thailand's traditional royalist establishment of generals and old-money families in Bangkok who have backed Mr Abhisit, a British-born, Oxford-educated economist who struggled to connect with working-class Thais even as he was lauded by investors.
At the heart of Ms Yingluck's support is the red-shirt movement that accuses the rich, the establishment and top military brass of breaking laws with impunity - grievances that have simmered since a 2006 coup overthrew her brother.
Mr Thaksin, a former telecommunications tycoon, scored landslide election wins in 2001 and 2005 by appealing to the rural poor with populist policies, from cheap credit to universal healthcare. Ms Yingluck electrified his supporters and ran a disciplined campaign.
Mr Abhisit (46), had warned of instability ahead if the opposition wins. He blamed the red shirts for last year's violence and has cast Mr Thaksin as an authoritarian crony capitalist. His backers - the royalist establishment and urban middle class - want Mr Thaksin to serve a two-year prison term for conflict of interest offences. They say his sister is a proxy for him and would clear the way for his return.
Mr Abhisit had hoped to win a mandate from the people after coming to power in a controversial 2008 parliamentary vote when a pro-Thaksin ruling party was dissolved by the courts. His Democrats have not won an election in nearly 20 years.
Throughout the six-week campaign, the two sides have presented similar populist campaigns of subsidies for the poor, improved healthcare benefits and infrastructure investment including high-speed rail systems across the country.
The election is Thailand's 26th since it became a democracy in 1932, ending seven centuries of absolute monarchy. It has since been governed by 17 constitutions and has experienced 18 military coups, either actual or attempted.