Former prime minister Somchai Wongsawat has registered to run for a Senate seat in Chiang Mai as the first day of candidacy registration got off to a busy start on Monday.
Mr Somchai was seen arriving at Mae Rim district auditorium in Chiang Mai to register his candidacy on Monday.
The former premier is the husband of Yaowapha Wongsawat, paroled ex-premier Thaksin Shinawatra's sister.
His decision to contest is believed to be made to facilitate his attempt to secure the Senate speaker post later, with the backing of the ruling Pheu Thai Party.
A source said Thaksin, who is believed to be the de facto leader of Pheu Thai, is planning to push Mr Somchai as the next Senate speaker, a post that could cement the party's power in the legislative branch.
Applications for the Senate election will be accepted until May 24. Each candidate must pay a 2,500-baht registration fee.
Members of the new 200-seat Senate will come from 20 professional groups, but will not be directly elected by the public. The applicants will vote among themselves in three stages, starting with intra-professional groups and then inter-groups at the district level. Successful applicants from various professions who emerge from the district-level polls will go on to cast inter-group votes at the provincial and national levels.
In Mae Rim district, at least 200 candidates registered for the race on Monday. Many were reported to be well-known local figures.
Chiang Mai election director Noppadol Suya said applications were likely to top 1,500 in Chiang Mai on the first day of registration alone.
It is among the provinces with highest number of applicants after Bangkok and Si Sa Ket, Mr Noppadol said.
Mr Noppadol warned reporters not to interview applicants, as under the Senate election law, candidates are forbidden from canvassing for votes.
Election Committee (EC) chairman Itthiporn Boonpracong said on Monday the commission has explained the voting rules in detail to all agencies dealing with the election.
In Bangkok alone, more than 5,000 officials were on hand to assist with the application process, he noted.
Meanwhile, Manoch Nakkerd, an applicant, said the 2,500-baht registration fee is too high. He said the fee may deter some people from applying, noting the fee should be lowered to 500-1,000 baht.
A source said the registration system was down on Monday morning, but the issue was rectified soon after.