The Election Commission has confirmed there was a huge turn out for advance voting on Sunday, with 86.98% of about 2.6 million people who had registered casting their votes.
Chairman Ittiporn Boonpracong said on Monday that polling unit-based turnouts were above 90% in many provinces and the EC had to keep some units open beyond the official closing time of 5pm to let all voters exercise their right.
For example, polling booths in Bang Kapi district of Bangkok remained open until about 6pm. About 52,500 people showed up there.
The EC suspected electoral fraud in Samut Songkhram province, where some ballots had been marked in advance. They had been destroyed and new unmarked ballots readied for issuing to the voters before advance polling started.
In Kalasin province, documents were forged to claim that some candidates had been disqualified. In Uthai Thani province, some people tried to use the ID cards of other people to cast votes, Mr Ittiporn said.
There was a glitch when the EC's Smart Vote phone app stopped functioning at 8.30am, but it was back up and operating again 15 minutes later, he said.