BANGKOK, July 10 (Reuters) - Thailand's Election Commission on Wednesday endorsed 200 new senators who will replace a military-appointed upper house, revealing a new legislative body that analysts say could make it harder for the embattled ruling Pheu Thai party to govern.

The new upper house will not have a role in voting to approve who becomes prime minister, but will retain the power to vet laws and appoint crucial members of powerful organisations like the Election Commission and the Constitutional Court.

Election Commission Secretary-General Sawaeng Boonmee said that there had been a delay in announcing the results of a complex senate selection process that ended last month because of a number of complaints, which have now been examined.

"The Election Commission has passed a resolution to endorse 200 senators," Sawaeng told reporters.

Provisional results of the senate selection showed an upper house lacking key Pheu Thai affiliates, while marking a gain for its largest coalition partner, Bhumjaithai, which could act as a proxy for the conservative-royalist establishment, analysts said.

A rift between the conservatives, backed by the military, and populist parties like Pheu Thai has long defined Thailand's politics, sometimes triggering violent street protests and military coups in 2006 and 2014.

"The election of a new Senate was a chance to turn a new page and allow a more Pheu Thai-friendly senate to take office," said Mathis Lohatepanont, an independent political analyst.

"This possibility was not realised."