Wissanu Krea-ngam, a legal adviser to the prime minister, on Tuesday expressed concern about accusations that the Senate election is being marred by irregularities.
But while problems were detected in the district-level voting on Sunday, they were relatively minor ones, he said.
The Election Commission (EC) said voting in most districts went smoothly as there were not many applicants, Mr Wissanu said.
“However, when the voting at provincial and national levels takes place, there may be a reason to worry,” he added without elaborating.
Caretaker senator Somchai Swangkarn on Tuesday called on the EC to disclose detailed results of the district-level voting amid the complaints.
He said several candidates had asked to see the poll results, but district election officials had rejected their requests, saying they had already sent the results to the EC.
Mr Somchai has repeatedly claimed there are concerted attempts to manipulate the outcome of the Senate election.
He said earlier that a review of Sunday’s results showed that many applicants had failed to receive any votes while others had received overwhelming support.
Mr Somchai, who chairs the Senate committee on human rights and consumer protection, said this stemmed from a loophole in the organic law governing the election, which allows candidates to vote for themselves and/or for other candidates.
He alleged some of those who received no votes on Sunday may have been bankrolled to join the race by a political party or interest group, simply so they can vote for other candidates.
“For example, the Senate committee has received information that a resort owner who applied to run in the election told his employees to apply as well,” Mr Somchai said.
He blamed the EC for failing to thoroughly examine the candidates’ backgrounds, saying many are believed to have lied about their professional experience.
He also claimed that in the next round of provincial-level voting on June 16, it would become clear that several individuals were hired to take part, simply to vote for candidates backed by certain political parties or interest groups.
A total of 23,645 candidates from 20 professional groups have qualified for the second round of polling. The winners will move on to the national vote on June 26 to select 200 members of the upper house.