A Thai officer shows a ballot during vote counting at polling station in Bangkok, Thailand, Sunday, May 14, 2023. Vote counting was underway Sunday in Thailand s general election, touted as a pivotal chance for change nine years after incumbent Prime Minister Prayuth Chan-ocha first came to power in a 2014 coup. AP
With votes counted from just over a quarter of polling stations, the reformist Move Forward Party (MFP) was on nearly two million votes, followed by Pheu Thai on 1.8 million, according to Election Commission figures.
The numbers are broadly in line with pre-election opinion polls which forecast success for the opposition and heavy defeat for Prayut.
Pheu Thai is the latest iteration of the political movement founded by billionaire former premier Thaksin Shinawatra that has dominated Thai elections for two decades.
But MFP has grown rapidly, fuelled by the youth-led protests that erupted across Bangkok in 2020 to demand democratic change and reform to Thailand's untouchable monarchy.
Prayut's United Thai Nation party lay in third place with around 700,000 votes.
Pheu Thai and MFP still face a battle to take power because the prime minister will be chosen not just by the 500 elected MPs but also by 250 senate members handpicked by the last military junta.
Thailand has seen a dozen coups since 1932 and there are fears an unclear or disputed result could lead to fresh military intervention or street protests.