BANGKOK (AFP) - The billionaire leader of the newest and most dynamic force in Thai politics says he is "prepared" for jail as legal cases besiege his youth-focused party just weeks after it scooped up millions of votes in a general election.

Thanathorn Juangroongruangkit, the charismatic political newcomer whose radical agenda of social and economic reform captured millennial hearts and rattled the ruling junta, will appear at the Election Commission later on Tuesday (April 30) to explain a disputed share transfer.

It is the latest of a battery of moves against Thanathorn and his Future Forward Party, which secured over six million votes in March 24 elections, but is now hemmed in by 16 separate legal cases.

"I knew from the day we launched the party that the threats would come sooner or later," he told AFP on Monday from his mansion in a Bangkok suburb.

"It is sooner than we thought."

The commission poses a real and immediate challenge.

It is expected to rule over coming days on an allegation that Thanathorn breached election rules by owning shares in a media company.

The 40-year-old insists the shares were divested weeks before he registered to run, rubbishing the charge as a political hatchet job.

The commission can suspend Thanathorn from political activity - a potential gut punch to his nascent movement, which relies heavily on his star power and the social media conversation he has started with younger voters.

It could also forward his case to higher courts, which carry heavy jail sentences for breaching election rules and can ultimately disband the party.

He also faces a sedition charge with a potential seven-year jail sentence. But Thanathorn struck a defiant note as his powerful political enemies circle.

"I'm prepared mentally and physically for whatever comes," the scion of an auto-parts fortune said.

'TIME IS WITH US'

Future Forward has shaken up the Thai political landscape - long framed by loyalty to the royalist, conservative establishment or the populist and self-exiled ex-premier Thaksin Shinawatra.

March's poll was the first since Thailand's junta seized power in 2014.

But a new government has yet to be declared amid allegations of vote-rigging and other political chicanery by the junta-allied party, which is desperate to return to power with a majority of Lower House seats.

"The military government will do whatever it takes to stay in power. They are willing to rig the election and use legal threats," Thanathorn said.

The junta and its political allies deny the accusations.

The pro- and anti-military camps are striving to form a coalition to reach the magic mark of 250 Lower House seats - a majority to form a government.

Neither bloc had a commanding lead after preliminary results.

The Election Commission has said it will announce near-complete results on May 9.

Critics say the inexplicable delay in announcing full results is allowing political loyalties to be traded and seats to be chipped away.

Future Forward, now Thailand's third largest party, says several of its candidates have been approached in recent weeks with cash inducements of over US$1 million (S$1.36 million) to defect.

While the legal assaults have put a pin in the elation that followed their shock poll showing, Thanathorn remains confident of the long game against an ageing out-of-touch junta and its establishment allies.

"These people (the junta) don't want to see the future. But time is with us."