FILE PHOTO: An electoral staff member shows a ballot during vote counting at the general election in Mae Hong Son, Thailand, March 24, 2019. REUTERS/Ann Wang

BANGKOK (Reuters) - Thai election officials said they would announce the winners of 350 parliamentary seats on Monday and more details of those contests would come on Friday, but a clear picture of the lower house’s 500 seats could take weeks to emerge.

A drawn-out process could complicate coalition-building to form a government, five years after a military coup.

A pro-army party is seeking a democratic mandate for junta leader Prayuth Chan-ocha to keep the premiership.

Already on Monday anti-junta parties claimed that there had been irregularities in Sunday’s election after partial results showed that the pro-army party was leading the popular vote.

The Election Commission said it would name the winners of 350 constituency seats of the 500-seat lower house of parliament, the House of Representatives, on Monday.

A voter breakdown of those constituency contests would not be available until Friday.

“Today we will only see the names of the winners in 350 constituencies,” Jarungwit Pumma, secretary-general of the Election Commission, told a news conference. “Numbers are still moving. We can’t publish them now. Please wait a couple of days.”

A further 150 seats that will be allocated on the basis of a complex formula involving voter turnout won’t be announced until May 9. However, if there is enough detail in Friday’s numbers it might be possible to extrapolate the winners of the 150.