The Election Commission (EC) faced heavy criticism after officials at one advance voting station gave wrong details on constituencies and provinces of cast ballots on Sunday.
EC secretary-general Sawaeng Boonmee said officials at the Nonthaburi advance voting station wrote incorrect details about the constituencies and provinces of voters on parcels of used ballots. The mistakes were found after about 100 people had cast their votes there.
After learning of the errors, election officials corrected them and there would not be any problem about vote counts for any constituencies and provinces on the election day on May 14, Mr Sawaeng said.
"I confirm that the used ballots will be sent to their respective constituencies... The incident was the fault of our officials. An investigation will determine if these were honest mistakes," the EC secretary-general said.
He said that the mistakes would not recur on the election day next Sunday because voters would cast ballots at their respective polling stations, unlike at advance stations on this Sunday.
Social media users expressed their frustration over the mistakes. Many people demanded legal action against election commissioners, including their impeachment.
