Thai Princess Ubolratana was put forward Friday as a candidate for prime minister in the March elections, the first time a royal has entered frontline politics - a development the palace later condemned as "highly inappropriate".
The party, which is allied to divisive former Prime Minister Thaksin Shinawatra, said in a statement that it would submit to the royal order out of loyalty and respect towards the members of the royal household, Efe news reported.
A former general, Mr Prayuth also announced on Friday that he would be running for prime minister in the forthcoming election as a candidate for the pro-military Palang Pracharat party.
In this March 24, 2010, photo, Thai Princess Ubolratana poses for a photo during her visit to promote Thailand's film industry at the Entertainment Expo Hong Kong Filmart.
In 2016, Thais voted to approve a new constitution created by the country's military leaders, which was designed to perpetuate military influence and block Mr Thaksin's allies from winning another election. She lived in the United States for more than 26 years before they divorced in 1998.
Both Thaksin and Yingluck live overseas as fugitives on corruption charges they say are politically motivated.
The Thai Raksa Chart Party has cancelled plans today to launch their election campaign in Bangkok's China Town.
Because Thailand is a constitutional monarchy, the king and other royal family members are not supposed to get directly involved in politics.More news: Bob Stoops Named Head Coach of Dallas XFL Franchise
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King Rama X made a televised address about his sister on Friday saying, "Involvement of a high-ranking member of the Royal Family in politics, in whatever way, is an act that conflicts with the country's traditions, customs and culture and therefore is considered extremely inappropriate".
2001: Ubolratana and her children permanently return to Thailand.
"I am not aiming to extend my power but I am doing this for the benefit of the country and the people", he said.
Ubolratana, whose official name is considerably longer than that under which she was registered with the Election Commission, is the first-born child of the late King Bhumibol and Queen Sirikit. 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.
The Thai Raksa Chart Party was launched in November by relatives and supporters of the Shinawatras.
Ubolratana, who is active on Instagram, did not directly mention the king's order in a Saturday message, merely thanking people for their support and encouragement and insisting on her honest desire to see Thailand progress with rights and opportunities for all its people.
But Ubolratana's shock entrance into politics, aligned with the junta's nemesis - the Shinawatra family - undercuts those claims.
While the monarchy, which is vastly wealthy and protected from criticism by harsh royal defamation law, has been seen as above the political fray, royals have intervened in moments of political crisis.
2004: Ubolratana's son, Bhumi, is killed in the Indian Ocean tsunami.