A Thai political party will prevent a princess from running for the prime minister position in March elections, it said on Saturday, marking a dramatic U-turn after it said it would nominate her for the position.
"Thai Raksa Chart party complies with the royal command", it said in a message to reporters.
The statement added that the party is ready to do its duty with respect to the "tradition and royal customs" under Thailand's constitutional monarchy.
The announcement effectively prohibits Princess Ubolratana's unprecedented bid for prime minister in March elections and comes after an extraordinary rebuke of her candidacy by her younger brother Thai King Maha Vajiralongkorn.
Thai Raksa Chart announced the princess as their candidate on Friday morning in a move that looked to rattle the status quo and threaten the ambitions of the junta that has ruled Thailand since it toppled the administration of Yingluck Shinawatra in a 2014 coup.
But the Thai king torpedoed the bid in a sharply worded statement later the same day that said bringing senior royal family members into politics is against tradition, national culture and "highly inappropriate."
Thailand has some of the most severe lese majeste laws in the world and the king's word is considered final.
Analysts had already forewarned that the palace statement had scuttled the princess' chances.
"The palace disapproval invalidates her candidacy," said Puangthong Pawakapan, professor of political science at Chulalongkorn University, before the Thai Raksa Chart announcement.
Thailand is a constitutional monarchy and has not had a royal run for frontline office since 1932.
The 67-year-old princess did not address the royal rebuke head-on Saturday morning, when she thanked supporters on her widely followed Instagram account and said vaguely that she wanted Thailand to "move forward".
Junta chief Prayut Chan-O-Cha, the leader of the coup that toppled the administration of Yingluck Shinawatra, also said he would stand for the top post Friday.
Ubolratana's move briefly threw his fortunes into disarray but the palace action made it clear it does not endorse her run.
The king did not criticise the princess directly and seemed to focus blame on political party members who brought her on board.
Thai Raksa Chart is aligned with Yingluck and her brother Thaksin, who was ousted by the army in 2006.
Analysts assumed Thaksin and the party would not make such a move without royal approval.
She has disregarded royal tradition before – most notably by marrying an American fellow student, Peter Jensen, while studying at the Massachusetts Institute of Technology (MIT) when she was 21 years old.
The princess was required to give up the titles Her Royal Highness and Chao Fa (Lady of the Sky), which were bestowed on her birth in 1951 in Switzerland, where her father, King Bhumibol Adulyadej, was attending university.
After her marriage and 1973 graduation from MIT, she moved with her family to California and used the name Julie Jensen, earning a master's degree in public health at the University of California, Los Angeles.
She had three children – daughter Ploypailin Jensen, son Bhumi Jensen and younger daughter Sirikitiya Mai Jensen.
She lived in the United States for years, though frequently visited her parents, the much-revered King Bhumibol, who died in 2016, and Queen Sirikit.
Ubolratana grew up close to her father and during her teens shared his love of sports, becoming his favourite partner in tennis, badminton and small-boat sailing. The pair shared a gold medal in sailing at Southeast Asian games in 1967.