Thailand’s conservative establishment is seeking to exterminate politicians who promised reform, according to the former leader of a popular party that was banned by the courts last week.

Pita Limjaroenrat, whose Move Forward party won the most votes and most seats in last year’s election, said Thailand was trapped in a “double lock democracy” where the legal system and military coups were repeatedly being used to undermine election results.

His former party was dissolved on Wednesday over its promise to reform the country’s strict lese majesty law, under which criticism of the monarchy can lead to up to 15 years in prison.

UN Human Rights Chief, Volker Turk, the European Union and the US state department all expressed concern over the Constitutional Court judgment, warning it set back the country’s democratic progress.

The party’s remaining MPs have since regrouped under a new party, the People’s Party, but Pita and the executive committee of Move Forward are banned from politics for 10 years. He has warned legal threats against the new party could escalate.

“They’re coming after us. They’re exterminating us,” said Pita, who spoke to the Guardian from his home in Bangkok. “They’re not going to compromise. They’re not here to find consensus.”

Move Forward had promised to shake up Thailand by stopping the military from intervening in politics, breaking up monopolies that dominate the economy and reforming the lese majesty law.

Their pledges resonated with a wide cross-section of Thai voters, but also attracted fierce opposition from members of the powerful military royalist establishment, which blocked it from taking power, accusing it of trying to overthrow the monarchy.

Pita said his opponents were using the monarchy as a pretext to protect their own interests.

“I believe the king is revered above politics as we are a constitutional monarchy,” he said, adding that he hoped, “the people in power, whether it’s military or monopolies, stop dragging down the monarch as an excuse to protect their concentration of wealth and power.”

The party’s pledge to reform the law was aimed at de-escalating conflict that has existed between younger generations and the monarchy, he said.

“My attempted amendment of the criminal code [article] 112 [the lese majesty law], was hoping to use the parliament as a middle path, a common ground, with transparency.”

In 2020, mass youth-led protests called for reform of the monarchy, criticising an institution that had long been considered untouchable. In the run up to last year’s election there was unprecedented discussion of lese majesty, with political parties forced to announce their stance on the law. Move Forward was the only party to promise reform.

There is now a shrinking space for such debates, Pita said, adding that the conditions for free speech were worse today than even before the mass protests began. Since 2020 at least 272 people have since been charged with lese majesty.

Pita said that there was “a thirst for justice” among the public after the dissolution of Move Forward. “I spend my time trying to shape the trajectory of anger and thirst [towards] the ballot box, rather than the battles on the street,” he said, adding that street protests brought the risk of “bullets in people’s heads” and of a military coup.

The Thai authorities have a history of using excessive violence against protesters, including in 2010, when at least 90 people were killed in a military crackdown.

The threat of a coup was always a possibility in Thailand, he added. “I speak that not because of my feeling but because of facts … From 1932… there have been 13 military coups and 20 attempted [coups] … the last one being just a decade ago,” he said. Judicial harassment was the other way in which the establishment maintained control, he added.

Move Forward was the 34th political party to be dissolved since 2006, according to Pita.

Further legal threats loom against former Move Forward MPs, including those who have moved to its successor, People’s Party. The National Anti-Corruption Commission is investigating the ethical conduct of 44 politicians who belonged to Move Forward who supported the bill to reform lese majesty. They could face a lifetime ban from politics.

The new party would aspire to win by an even greater margin than in last’s year’s election, “to the extent that we’re the undisputed leader in a democratic Thailand”.

The old structures that exist in Thailand also risked a “collapse from within”, he added, as newer generations enter politics, the legal system or the military.

The People’s party has said its ideology remains unchanged, though its strategies may differ. “You can pick up a few flowers, but you cannot stop spring,” Pita said.