Princess Ubolratana Rajaka of Thailand attends "Thailand Hub of Entertainment", a film and entertainment industry event for investors, in Hong Kong.
Princess Ubolratana, the glamorous older sister of King Maha Vajiralongkorn, announced last week her unprecedented decision to run for the top job in March.
The focus was on Thai Raksa Chart after its nomination of Princess Ubolratana as its PM candidate and the royal announcement was issued hours later that no royal family member could get involved in 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.
Also know as Ubol Ratana, the princess renounced her royal titles when she married a U.S. citizen in 1972, but was given them back after her divorce and return to Thailand in the late 1990s.
"All members of the royal family must abide by the king's principle of staying above politics, maintaining political impartiality and they can not take up political office", part of the statement released to the media said. The commission is likely to follow the wishes of the monarch, who holds a semi-divine place in Thai society.
"I think the party leader and board should take a responsibility by resigning", said Srisuwan Janya of the Association for the Protection of the Constitution, a royalist activist group, who submitted a petition to election authorities Monday calling for the party's censure.
Thai Raksa Chart's Executive Chairman Chaturon Chaisaeng declined to comment on Sunday on the request to disband the party.
Thailand's junta chief on Monday dismissed rumours of an impending coup as "fake news", as speculation ricocheted across a kingdom unsettled by the ill-fated political union between a princess and a party allied to the powerful Shinawatra clan.
It said the monarchy was above politics and described his sister's candidacy as "highly inappropriate".
"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".
Mr Prayut overthrew the democratic government of Yingluck Shinawatra, the younger sister of former Prime Minister Thaksin Shinawatra.
Thai Raksa Chart is one of several pro-Thaksin parties contesting the election. The takeover resulted in the installation of a junta intent on eradicating the influence of former Prime Minister Thaksin Shinawatra, whose allies have won every national election since 2001.