The move from the Thai Raksa Chart party is broadly speculated to have been engineered by former PM Thaksin in the fugitive's ongoing interference, in exile, with Thai politics.
The announcement means a royal-fronted party tied to the Shinawatras will directly take on the military party, whose own candidate was also announced Friday as junta leader Prayut Chan-O-Cha.
Thailand's tense political scene was thrown into further uncertainty today when a princess was declared a candidate for prime minister in next month's elections, in competition with the ruling dictator.
In an online post titled "Thank you", the former royalty said she is exercising her political rights as a commoner by contending atop Thai Raksa Chart Party's ticket.
The election, despite the smokescreen of "national conciliation" is still seen as a battle between Thaksin's populists (the Red Shirts) and allies of the royalist-military establishment (the Yellow Shirts).
Ahead of the elections on March 24, Princess Ubolratana's move would be seen as one that could change the dynamic of Thailand's already uneasy political system.
Thailand became a constitutional monarchy in 1932 but the royal family wields great influence and commands the devotion of millions of Thais.
"The board agrees that the name of Princess Ubolratana, an educated and skilled person, is the most suitable choice", Thai Raksa Chart party leader Preechapol Pongpanich told reporters.
But the pro-Thaksin side was always likely to win the largest share of the seats; with a royal candidate for prime minister it has an additional, significant advantage, given the nearly instinctive reverence for royalty among many Thais.
"In everything we do we must devote our heart, our knowledge, every part of ourselves", she said in 2017 in a speech to mark her father's birthday.
The princess was stripped of her royal title when she married a United States national in 1972.
The Election Commission is required to endorse or reject all candidates by next Friday.
He said: "I am not aiming to extend my power but I am doing this for the benefit for the country and the people".
Prayuth accepted his nomination from the Palang Pracharat Party, a new party set up by his loyalists, in an official statement. She studied mathematics and bio-chemistry at MIT and earned a master's degree in public health from the University of California at Los Angeles.
Beyond her royal appearances at charities and events, Princess Ubolratana is an avid social media user who has close to 100,000 followers on her personal Instagram page.
Her son was killed in the Indian Ocean tsunami in 2004. After living in the USA for 26 years, she returned to Thailand in 2001 following her divorce.
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