The Thai royal family, a revered institution shielded from criticism by a tough defamation law, has traditionally been seen as above the political fray, although royals have intervened in moments of political crisis.
Thailand's king has crushed the plans of his older sister to become a candidate for the country's prime minister.
Still, Paiboon Nititawan, the pro-military People Reform Party leader, has called on the Election Commission to meet Monday to consider dissolving the Thai Raksa Party for nominating the princess despite withdrawing her nomination.
Ubolratana was stripped of her royal title when she married a USA national in 1972.
In a statement read on all Thai television stations within hours of Ubolratana's announcement as a candidate, King Vajiralongkorn said it was "inappropriate" and unconstitutional for members of the royal family to enter politics.More news: Barrie’s jobless rate rises slightly, remains below provincial average: Statistics Canada
The Election Commission on Monday afternoon declared that the eldest daughter of the late King Bhumibol can not compete in the upcoming election as a candidate for prime minister.
Thailand has been a constitutional monarchy since 1932, but the royal family wields great influence and commands the devotion of millions of Thais, with the king considered to be semi-divine.
Thailand's Electoral Commission announced on Monday that the "monarchy must remain above politics".
Ubolratana Mahidol has filled many roles in her 67 years, from Thai princess and royal rebel to Californian mother, pop singer, film actress, charity worker and flamboyant social media celebrity.
"I would like to say once again that I want to see Thailand moving forward, being admirable and acceptable by worldwide countries, want to see all Thais have rights, a chance, good living, happiness to all", she said, ending her post with an "#ILoveYou" hashtag.More news: Munro's fireworks help Kiwis beat India to claim T20 series
She gave up her royal titles after marrying an American and she has starred in soap operas and an action movie.
Thai Raksa Chart, the party that nominated the princess on Friday, said its executives will speak at a news conference at 5.30pm today. The military government's leader, Prayuth Chan-ocha, is also contesting the race for prime minister as the candidate of a pro-army party.
Srisuwan said his complaint to the Election Commission would ask it to recommend that a Constitutional Court dissolve the party.
Mr Prayut overthrew the democratic government of Yingluck Shinawatra, the younger sister of former Prime Minister Thaksin Shinawatra.
Thaksin, who was ousted in a 2006 coup, lives in self-imposed exile after being convicted of corruption in absentia.More news: Thai court orders release of Bahrain refugee soccer player
Dissolving Thai Raksa Chart could hand more seats to military-affiliated parties or other established parties, as well as a separate youth-oriented populist party.