The court decision on Wednesday came after it accepted a case that alleges Pita, leader of the election-winning Move Forward Party, was unqualified to run in a May 14 election because he held shares in a media company, in violation of electoral rules.
The 42-year-old, United States-educated liberal Pita lost his initial bid for the premiership in a parliamentary vote last week and needs the backing of more than half of the bicameral parliament to become the next prime minister.
He must overcome fierce resistance from rivals at odds with his party's anti-establishment ambitions, including a royalist military that appointed members of the Senate that denied Pita in his initial bid.
It was not immediately clear whether the court announcement would scuttle Wednesday's vote, with MPs still debating Pita's nomination.
Parliamentary rules written by the military after a 2014 coup and skewed in its favour are making it extremely difficult for Pita to form a government with an eight-party alliance that continues to back him.
The court decision, its second active case involving Pita, came as MPs debated whether Pita should be allowed to contest a second vote on the premiership, with political rivals arguing he had already been rejected.
Pita has argued he broke no rules by owning shares in media company iTV as it had not engaged in mass media operations for years.Â
He has 15 days to respond to the suspension, the court said in a statement.
Move Forward said the court ruling had no impact on proceedings.
"According to the law Pita remains a candidate for prime minister," it said, urging people to follow the televised debate.
Pita has a mountain to climb to become premier and Wednesday's twin challenges from both his political enemies and the court were hurdles he had been expecting.
In an interview on Tuesday, he told Reuters those moves were "pre-planned" and questioned the timing, describing efforts by the royalist military to thwart him as like a "broken record".
Thailand has been run by a caretaker administration since March and 65 days have passed since Move Forward's stunning election triumph over parties backed by the military after nine years of government controlled by generals.
