BANGKOK - Thailand's opposition Move Forward named a new leader on Saturday after Pita Limjaroenrat, who led the party to a stunning election victory in May, was thwarted in his efforts to become premier.

Chaithawat Tulathon, a former political magazine editor, will head Move Forward, which won the most seats in parliament on a wave of youth and urban support over its anti-establishment policies. The progressive party will lead the opposition after conservative lawmakers and an unelected senate blocked its attempts to form a government.

Pita stepped down as party leader earlier this month amid a host of legal and legislative challenges that many see as part of a pattern by the pro-military and royalist establishment to diminish a new generation of leaders.

In July, he was suspended from parliament over allegations he owned shares in a media company, making him unfit for office. Pita denies this.

Chaithawat, who was previously the party's secretary-general, called the move a "temporary restructuring" while Pita clears his name. Pita would continue on as advisor to the party and manage activities outside parliament, Chaitawat said.

Earlier this week, the courts banned a prominent Move Forward party supporter, Pannika Wanich, from politics for life over a photo she posted online more than a decade ago that was deemed disrespectful to the monarchy and in breach of ethical standards.

Move Forward has pledged to amend the country's harsh royal insult law which penalises perceived slights against the monarchy with up to 15 years in prison.

The country's constitution, drafted during junta rule, has "become a potent tool to arbitrarily attack outspoken politicians," Sunai Phasuk, senior researcher on Thailand for Human Rights Watch told Reuters.

"This could easily wipe out members of the opposition, who give commentary calling for reforms," he added.

(Reporting by Chayut Setboonsarng and Panu Wongcha-um, Edited by Kanupriya Kapoor and Simon Cameron-Moore)