By Panu Wongcha-um and Chayut Setboonsarng

BANGKOK Thai prime ministerial candidate Pita Limjaroenrat on Tuesday said he was willing to slow the pace of his party's ambitious reform agenda if he forms a government but would not retreat from its plan to amend a law prohibiting royal insults.

In an interview with Reuters, the leader of the election-winning Move Forward party described efforts by the military establishment to block him as like a "broken record" and said Thailand had entered a different era with the public hankering for change.

Pita, 42, will contest a parliamentary vote on the premiership on Wednesday for the second time, after failing last week to win the required backing of more than half of the legislature, as the conservative, military-appointed Senate closed ranks to deny him the top job.

"It was absolutely expected, the same thing, same venue. Broken record. But the sentiment of the era has changed," he said in the interview.

"Despite what happens tomorrow there has been progress in society. They demand something new, something fresh."

Move Forward was the surprise winner of the May 14 election, capitalising on massive youth support to defeat conservative rivals in what was seen as a resounding rejection of nearly a decade of government led or backed by the military.

The party's plans to tackle business monopolies, end conscription in the military and remove generals from politics are controversial, but none more so than its aim of changing article 112 of the criminal code, which punishes insults of the monarchy by up to 15 years in jail.

Pita said he would be flexible and the decision was ultimately one for parliament to decide, but his party would not back away from its reform agenda just to seek smooth passage to office.

Amending 112 was not a threat to the palace, he said, but would ensure the monarchy was not politicised and that the law, under which hundreds of people have been charged, should not be misused.

"I'm still sticking to what I promised the voters ... the institution is above politics. That's the only option for governance in this country,' he said.

He added: "I cannot look them in the eye if I'm walking away from this issue."

The military has for decades invoked its duty to defend the monarchy to justify intervention in politics, and used the law against royal insult to stifle dissent, critics say.

(This story has been corrected to add the dropped work 'era' in paragraph 2)

(Reporting Panu Wongcha-um and Chayut Setboonsarng; Writing by Martin Petty; Editing by Robert Birsel)