Last week, a party allied with Thaksin said its candidate for prime minister, if it were it to win the election, would be Princess Ubolratana Rajakanya Sirivadhana Barnavadi, the king's older sister.
The announcement caused a sensation in a country where the royal family has traditionally remained above the political fray.
Hours later, King Maha Vajiralongkorn made clear his opposition to his older sister's political foray, calling it "inappropriate" and unconstitutional.
Thailand has been a constitutional monarchy since 1932, but the royal family wields great influence and commands widespread devotion, with the king considered to be semi-divine.
The election commission disqualified the princess on Monday and on Wednesday said it also aimed to dissolve the Thai Raksa Chart party, which nominated her.
The party was one of several set up by Thaksin's loyalists as back-up parties in case his main Pheu Thai party is disqualified for some reason.
The election commission said in a statement the Thai Raksa Chart party had violated an electoral law with its nomination of the king's sister, which was "antagonistic toward the constitutional monarchy".
"Therefore, it is agreed that a petition will be submitted to the Constitutional Court to consider dissolving the Thai Raksa Chart Party," it said in a statement.
Thai Raksa Chart officials told reporters the party did not violate the electoral law and it would ask the Constitutional Court to be "merciful".
The court said it would decide on Thursday whether or not to accept the case.
If found guilty, the party would be dissolved, and its board members would be banned from standing for political office.
That would take one of the Thaksin-linked parties out of the running.
Parties loyal to Thaksin, a former telecommunications tycoon, have defeated pro-establishment parties to win every election since 2001.
Ubolratana apologised on Tuesday for causing "problems" for the people.
"I am sorry my genuine intention to work for the country and Thai people has caused such problems that shouldn't have happened in this era," she said on Instagram after making a public appearance in central Thailand.
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.
Some social media users urged her to serve the people as a member of the royal family, but Ubolratana responded: "I don't want to be in that position anymore. I gave that up a long time ago."
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