The rejection is a setback for the opposition Democrat Party, which has aligned itself with protesters trying to oust the government of Prime Minister Yingluck Shinawatra, the New York Times reported.
A related petition the Democrat Party filed with the country's Constitutional Court was still alive, leaving results of Sunday's election up in the air after protesters blocked registration and voting in Bangkok and southern Thailand.
An unnamed aristocrat who participated in the military-installed government after the 2006 coup Thursday called on Yingluck to step down, an act the government said couldn't be taken until a new government is formed, the Times said.
The Election Commission hasn't announced a plan to complete the election.
The Times said both sides have been weakened by the drawn-out protests that began as an anti-government movement and morphed into a campaign to block the election.
Protesters still blocked key intersections in Bangkok, but have pulled back from other areas and attendance at the rallies has tapered off, the Times said.
Prayuth Chan-ocha, the head of the army, said this week he wouldn't do anything "beyond the limits," a statement Thai media took to mean he wouldn't stage a coup. But, the army chief said, "I would rather not say whether I approve of the election."
Veerapong Ramangura, an economist who served numerous Thai governments, said during a television interview, an "agreement" to stage a coup fizzled because the former army general who was to have been installed refused to go ahead with the plans, the Times said.
"The protest leaders are now stuck," Veerapong said. "They don't know how to back out of this."