Pita Limjaroenrat resigned as a party leader from Thailand's Move Forward Party on Sep. 15.
Pita announced his departure on his Instagram and Facebook posts.
Why he resigned
According to Bangkok Post, Pita said that he is stepping down so that the party can select a capable MP to assume the role of the party leader who will also be the opposition leader.
Under existing laws, the opposition leader must be a Member of Parliament.
Pita was suspended from his MP role in July over his shareholdings in a media company.
'I haven't disappeared'
On his social media platforms, Pita also said he "[hasn't] disappeared" from politics.
He added that he would continue to work with Move Forward Party to drive change in his country.
View this post on Instagram
A look back on Pita's journey
The young 43-year-old was one of the hopeful candidates gunning for Thailand's Prime Minister position.
He was popular among young voters who were angry at the junta. The junta had been ruling Thailand for almost a decade.
Although he hadn't become PM in July, he invited pop star Taylor Swift to return to Thailand to perform after the 2014 coup d'état cancelled her concert.
Earlier this year during Thailand's May 14 general election, Pita's reformist Move Forward Party won the highest number of seats among all contesting parties.
However, he was prevented from becoming the prime minister by entrenched conservative political parties in parliament.
He was later suspended as a Thai member of parliament.
Thaksin's ally Srettha Thavisin of the Pheu Thai Party became Thailand's new prime minister instead on Aug. 22.
Meanwhile, Thaksin has returned to Thailand after his exile and is currently imprisoned.
His sentence has been reduced to one year by Thai king.
Top image from Pita Limjaroenrat - พิธา ลิ้มเจริญรัตน์/Facebook.