(CNN) Officials have disqualified a Thai princess from running for prime minister in next month's general election after her brother, King Maha Vajiralongkorn, said her nomination would be "inappropriate."

Thailand's Electoral Commission announced on Monday that the "monarchy must remain above politics."

In a shock announcement on Friday, Princess Ubolratana Rajakanya, 67, said she would stand as the prime ministerial candidate for the Thai Raksa Chart Party (Thai Save The Nation, or TSN) aligned with populist former leader Thaksin Shinawatra, who was ousted by the military in a 2006 coup.

The candidacy of a close member of the royal family is unprecedented in Thailand since the era of absolute monarchy ended 86 years ago.

Thai law stipulates that once a name is submitted, it cannot be withdrawn -- though the Electoral Commission has the power to decide the legitimacy of candidates.

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