At least four Pheu Thai Party executives have tendered their resignation from the party's board to avoid any possible political fallout from the Election Commission's (EC) probe into the role of former prime minister Thaksin Shinawatra in the Dec 20 local elections, said a party source.
According to the source, the individuals have also submitted letters to the EC to clarify they have nothing to do with the ex-premier's actions, which could put the main opposition party's future in jeopardy.
The former prime minister wrote letters, tweeted messages and spoke in video clips vouching for Pichai Lertpongadisorn, a former senator who contested and won the PAO chairmanship in Chiang Mai on Dec 20.
Critics of the Pheu Thai Party saw Thaksin's move as wielding influence over the party's affairs, which could lead to the dissolution of the party.
Firebrand activist Srisuwan Janya has petitioned the EC to investigate the matter.
The source said Pheu Thai members are concerned about the consequences of Thaksin's messages being reused during election campaigns to garner support for the party's candidate.
Thaksin's message was read by Mr Pichai during his campaign which was attended by Pheu Thai executives.
Mr Pichai won the PAO chairman race in an unofficial result, defeating arch-rival Boonlert Buranupakorn.
Thaksin also reportedly wrote a letter to woo voters into supporting Pheu Thai candidate Visaradee Techathirawat, who vied for the PAO chairmanship in Chiang Rai but lost.
His message appeared in Ms Visaradee's election campaign material.
A source in the EC said on Thursday that Chiang Rai poll officials had asked the EC if Ms Visaradee, by including Thaksin's message in her leaflets, had violated election campaign regulations.
In its reply, the EC said that in a case like this, a person who writes a letter vouching for a candidate is considered campaign staff.
Under local election rules, a candidate is legally required to submit a list of campaign staff members to poll officials prior to election day.
Thaksin was reportedly not listed as Ms Virsaradee's campaign staff. It is unclear what consequences will follow.
The source also said the EC expects to announce the first batch of PAO election winners early this month.