BANGKOK — Singapore will get a new president on Wednesday, but she will not be elected.

Halimah Yacob, 63, a former speaker of Parliament, will become the country’s first female president and the first in five decades to come from the Malay ethnicity when she is sworn in on Wednesday.

But what could have been a notable milestone for Singapore’s democracy is instead being publicly questioned as a rigged process, and her legitimacy is already coming under fire.

While Singapore’s Constitution does, in fact, provide for voters to elect their president, the eligibility requirements to stand for election were drawn so narrowly that only Ms. Halimah made the cut.

A Constitutional Commission, established by the prime minister, set the criteria, which were approved by Parliament. On Monday, Ms. Halimah was certified as the only eligible candidate, and since she has no opponent, there will be no election.