King Vajiralongkorn, 66, issued a message late on Friday, saying his elder sister’s candidacy was «inappropriate» and it was against the spirit of the constitution for royalty to be involved in politics.
While the Election Commission has the final say on approval of candidates, it seems unlikely its members would ignore the powerful influence of the king in making its decision.
In an Instagram post on Saturday, the princess did not directly mention her brother or her political hopes, but thanked supporters for their «love and kindness toward each other over the past day» and expressed gratitude for their support for her.
«I would like to say once again that I want to see Thailand moving forward, being admirable and acceptable by international countries, want to see all Thais have rights, a chance, good living, happiness to all,» she said, concluding with «#ILoveYou».
Thailand has been a constitutional monarchy since 1932, but the royal family has wielded great influence.
Friday was the last day for parties to declare candidates. Her main opponent in the March general election, if her nomination were to stand, would likely be Prime Minister Prayuth Chan-ocha, who was army chief when he led the 2014 coup and now heads the ruling junta, who also announced his candidacy on Friday.
The Election Commission declined to comment late on Friday night, with an official saying its members will hold a meeting on Monday.
The leaders of the princess’s nominating party, Thai Raksa Chart – an offshoot of the larger pro-Thaksin party that was ousted from power in the 2014 coup – have declined to comment on the king’s statement.
The party cancelled a planned event on Saturday in Bangkok featuring leader Preechapol Pongpanich, according to one of its parliamentary candidates. The princess had not been scheduled to appear at that event.
Ubolratana relinquished her royal titles in 1972 when she married an American, a fellow student at the Massachusetts Institute of Technology (MIT), Peter Jensen. She lived in the United States for more than 26 years before they divorced in 1998.