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.
He can run again if nominated in the next vote, which takes place on July 19, the house speaker confirmed.
Persons:
Pita Limjaroenrat, Chaithawat Tulathon, Pita, Vijay Vikram Kannan, Juarawee, Rae Wee, Tom Westbrook, Martin Petty
Organizations:
Senate, Harvard, Constitutional Court, Senators, Societe Generale, Thomson
Locations:
BANGKOK, Pita, Thailand, Asia, Singapore, Bangkok