Thanathorn Juangroongruangkit still faces a criminal charge of sedition for allegedly aiding protesters in 2015.

Thailand’s Constitutional Court has disqualified opposition leader and fierce government critic Thanathorn Juangroongruangkit as a Member of Parliament after finding him guilty of violating election law.

The leader of the Future Forward Party (FFP), was found on Wednesday to have broken election rules by owning shares in a media company while he campaigned in March’s controversial general election.

Thanathorn had denied the accusation, saying he transferred his shares in V-Luck Media before launching his campaign.

Despite the guilty verdict, Thanathorn will escape prison and a political ban, which supporters feared would hinder his party’s future prospects.

The 40-year-old billionaire is a strong opponent of the army’s role in politics and has been highly critical of the administration headed by former military government leader Prayuth Chan-ocha.

The FFP came a surprise third in March’s polls, proving particularly popular with young voters in the election that saw the pro-military party being declared the winner after a disputed ballot count.

Before Wednesday’s ruling, Thanathorn thanked supporters at the court and said: “The Future Forward Party is a journey … All of us will continue fighting and keep moving forward.”

Thanathorn’s now-vacant seat will be passed on to Manop Keereepuwadol, an FFP legislator, and the party has previously said it would push on regardless of the verdict. But some supporters were less assured about the party’s fortunes.

“Although I do not want it to happen, I believe it will be the beginning of the end for Future Forward,” said “O”, 25, an FFP voter and political science student at Bangkok’s Thammasat University, who declined to give his full name, told Al Jazeera before the court’s decision.

“It is unlikely that [FFP] would survive the upcoming constitutional court’s charges,” he said.

The party is part of an opposition alliance that disputed the vote count and accused the army of writing the electoral rules to ensure that Prayuth, a former army chief who in 2014 seized power from an elected government, would remain as prime minister.

The court had earlier suspended Thanathorn from parliament pending the verdict to this case.

The FFP leader also faces criminal charges, one for sedition for allegedly aiding anti-military government protesters in 2015.

A separate criminal charge against him for computer crime over a speech he posted on Facebook criticising the junta last year was dropped last month.