Junta-ruled Thailand held its first vote since a 2014 coup on Sunday, with a military-backed party and its main rival linked to a self-exiled billionaire both claiming the right to govern.
Full official results have not yet been released but questions are mounting over election irregularities that may have skewed initial numbers.
A Thai official said Thursday that nine people were arrested for sharing fake news on Facebook claiming two election commissioners had been sacked and that 600,000 illegitimate ballots were mixed into the vote count.
They were charged Wednesday under the Computer Crimes Act "for sharing or onpassing false information", said Siriwat Deephor, a spokesman for the Computer Crime Suppression Division Police.
"They confessed and said they didn't know that it was fake news," he added.
The accused face up to five years in jail and a $3,100 fine.
The Election Commission has said it would stagger announcements of the official results in the coming weeks, claiming "human error" in calculating ballots in some areas.
Preliminary figures show the military-aligned Phalang Pracharat party leading in the popular vote with nearly eight million ballots.
But its main rival Pheu Thai -- the party linked to former premier Thaksin Shinawatra -- has formed a seven-member coalition and claimed a majority of seats in the lower house.
In order to appoint a prime minister, the winning party must clinch more than half of the 750 seats in the combined lower and upper houses.
But all 250 seats in the upper house are military-appointed thanks to a charter passed by the junta, meaning non-aligned parties need an avalanche of votes to control the government.
The Election Commission is expected to release more results on Friday which could clarify the outcome of the vote.
Rights groups say the Computer Crimes law provides broad powers to crack down on online content and to target regime critics.
The head of the millennial-friendly Future Forward Party, poised to become Thailand's third largest faction, was accused of violating the act after a Facebook live broadcast criticised the junta last year.
A decision on whether to indict him and two other party members has been delayed until April.