BANGKOK: Thailand's election winning Move Forward party announced on Friday a plan to try to curb the power of the military-appointed Senate, a day after its members thwarted the party leader's bid to become prime minister.

The role of the 249-member Senate in deciding a prime minister along with the elected lower house - a system designed by the royalist military after a 2014 coup - is seen as a constitutional safeguard to protect the interests of the generals and the conservative establishment.

Despite being unopposed and with the backing of his eight-party alliance, Move Forward's Pita Limjaroenrat lost the crucial vote on the premiership on Thursday, after the Senate and parties of the outgoing, army-backed government closed ranks to deny him the top job.

Only 13 senators backed 42-year-old Pita, with the rest voting against him or abstaining, which his party said indicated some were acting under duress.

"There are forces from the old power to pressure the Senate - from the old power to some capitalists who do not want to see a Move Forward government," party secretary general Chaithawat Tulathon said in a television interview.

"Since the senators were uncomfortable in electing the PM, why not switch off this power?" he said, adding the party would attempt to limit the Senate's powers by amending an article of the constitution, which could take a month.

Pita, a Harvard-educated liberal from the private sector, has won huge youth support for his plan to shake up politics and bring reforms to sectors and institutions long considered untouchable.

That includes the monarchy, more specifically, a law that prohibits insulting it, by far Move Forward's most contentious policy and a big obstacle in its attempts to convince legislators to back Pita.

SUCKER PUNCH

Pita vowed on Thursday not to abandon those policies or give up his fight for the premiership. He can run again if nominated in the next vote, which takes place on July 19, the house speaker confirmed.

The Thursday defeat followed a sucker punch for Pita on the eve of the vote, when the election commission recommended he be disqualified over a shareholding issue, followed hours later by the Constitutional Court announcing it had taken on a complaint over his party's plan to amend the royal insult law.

The political tension this week had been widely expected.

Thailand has for two decades been locked in a power struggle between reform-minded parties that win elections and a nexus of old money and the military establishment determined to stifle them.

Pro-democracy groups have called for protests. One activist group, the United Front of Thammasat and Demonstration, took aim at the Senators and those who abstained in the vote, calling them spineless and "toxic to the will of people".

The uncertainty weighed on the Thai baht THB=TH, which slipped about 0.4% to 34.65 per dollar in morning trade. The benchmark Thai index .SETI was up 1%.

Vijay Vikram Kannan, Asia macro strategist at Societe Generale in Singapore, said the baht could underperform peers due to political risk, but a major selloff was unlikely.

"The market is just looking for an overall resolution of the situation. Whichever form it takes, that should lead to a rally," he said.