Nearly 38 million Thais voted in the February 8 election, which was won decisively by Prime Minister Anutin Charnvirakul's Bhumjaithai Party, allowing it to form a coalition government controlling more than 290 of the 500 seats in parliament.
The ruling on Monday averts the possibility of an election rerun and will be welcomed by Anutin, whose party is facing a challenge to win public trust amid a stuttering economy and allegations of corruption and involvement in rigging a selection process for the Senate, which it denies.
The decision had been closely watched in Thailand, where the Constitutional Court has been at the heart of two decades of intermittent political turmoil through verdicts that dissolved big parties, voided two general elections and brought down multiple governments and prime ministers.
The court case stemmed from a petition filed by the ombudsman that argued that barcodes and QR codes printed on ballot papers could be used to identify which candidate and party a voter chose.
The election commission had said the codes were used for security purposes and that identifying a voter would require access to ballot stubs that were stored separately.
The judges said that although barcodes on some ballots could potentially have been used to identify voters, they were included only for management purposes by election officials, with no intent to trace individual votes.
They said the arrangements for storing ballots, stubs and voter lists were "sufficiently safe".
The court nevertheless recommended against using such codes in future elections.
The same court voided a 2006 general election after finding the arrangement of polling booths compromised ballot secrecy and that the election had been called at too short notice.
It also annulled a 2014 election after anti-government protesters blocked some polling stations in Bangkok and the south, preventing voting from being held nationwide on the same day.
Those rulings both took place during periods of political tumult that led to military coups in the same year.
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