Mr Thanathorn Juangroongruangkit, leader of the progressive, anti-military Future Forward Party, was disqualified as an elected Member of Parliament (MP) by the Constitutional Court yesterday, a decision that could potentially create a domino effect on his party's survival and the overall political status quo.
His disqualification is effective from May 23, the judges said.
That was the day he was suspended as an MP after the Election Commission filed a case against him with the court for holding shares worth 6.75 million baht (S$304,000) in a media company.
Mr Thanathorn denounced the ruling as "giving more weight to assumptions rather than facts", and insisted he would remain the party's leader.
"The journey will go on. We will keep fighting," he said.
Maintaining his innocence and dismissing the charge as being politically motivated, Mr Thanathorn said he had sold his shares in V-Luck Media, a magazine publishing company, to his mother on Jan 8 and that the company had already ceased its operations before the electoral law came into effect on Jan 23.
But the judges deemed his defence to be "lacking weight" and "full of irregularities" as the share transfer was reported to the Commerce Ministry only on March 21.
He had registered as an MP candidate in early February.
Dr Yuttaporn Issarachai, a political science professor at Sukhothai Thammathirat University in Bangkok, told The Straits Times: "Thanathorn is the icon of Future Forward. Without him, their movement would be less influential."
He added that Mr Thanathorn's disqualification could have a ripple effect on his party's stability and very survival, as the ruling can be used by the Election Commission to file a criminal case against him with the Supreme Court.
The politician faces jail time of up to 10 years if he is found guilty of running for office knowing that he was in violation of election regulations. This sentence can, in turn, be used by the party's opponents to seek its dissolution and a political ban for its executives.
"But even without their representation in Parliament, the party members can still continue their anti-NCPO activism. Their momentum won't be lost," he added, referring to the party's vocal opposition to military rule.
The National Council for Peace and Order junta held power from the time of its 2014 coup until the first half of this year.
Future Forward surprised many by winning 80 seats in the March General Election - the first election since the coup - making it the third-best performing party despite being founded only last year, and the fact that none of its members had run for office before.