Image copyright Reuters Image caption Thanathorn Juangroongruangkit watched the court's announcement at his party's headquarters in Bangkok

A popular pro-democracy party in Thailand has been dissolved over a loan it received from its leader.

The constitutional court ruled a loan of around $6m (£4.6m) to Future Forward from Thanathorn Juangroongruangkit was a donation, and therefore illegal.

Mr Thanathorn, a wealthy young businessman who is critical of the government, established the party in 2018 to contest last year's election.

It performed unexpectedly well, winning more than six million votes.

Future Forward had garnered the third largest share of seats in parliament with 80 MPs.

Mr Thanathorn and other party executives have also been banned from politics for 10 years and will lose their MP status, Thai TV said.

The party's remaining 70 MPs have 60 days to switch to a new party in order to preserve their MP status, it added.

Mr Thanathorn argues the party was given no other opportunity to raise funds to fight the election.

Mr Thanathorn and his party have been hit with multiple lawsuits, which he says are politically motivated, reports the BBC's Jonathan Head in Bangkok.

Last year's poll ended five years of military rule, and saw the emergence in June last year of a coalition led by Prime Minister Prime Minister Prayuth Chan-ocha, the former junta leader who first took power in a 2014 coup.

Who is Thanathorn Juangroongruangkit?

At 41, he is the young and charismatic head of the Future Forward Party.

Mr Thanathorn, who is heir to a car parts business, has emerged as one of the fiercest critics of the prime minister. Last year, he faced charges of sedition.

His party won seats on a radical platform that appealed in particular to younger voters, giving it a sizeable voice in the first post-coup parliament.

It promised sweeping reforms, in particular of the military, which has seized power a dozen times in the past 70 years.

It has since joined a "democratic alliance" to try to prevent Prime Minister Prayuth from staying in power.

Thailand has been buffeted by political instability for years, largely a battle between supporters of the military and former Prime Minister Thaksin Shinawatra.