The Thai political party whose stunning decision to nominate the king's sister as its candidate for prime minister backfired when the monarch forbade her to do so has sworn loyalty to the king and thanked his sister for her effort.

Thailand woke up Saturday with a political hangover, pondering why Princess Ubolratana Mahidol agreed on Friday to be a candidate for the Thai Raksa Chart Party — breaking with tradition proscribing the monarchy's involvement with politics. Before the day was over, King Maha Vajiralongkorn invalidated the action, calling it "inappropriate" and unconstitutional.

Ubolratana's candidacy would have pitted her in the March 24 election against the preferred candidate of the pro-royalist military, Prime Minister Prayuth Chan-ocha, who led the 2014 ouster of an elected government.