The announcement came just months after Sineenat Wongvajirapakdi, 34, was made a royal noble consort by the king in July, the first such appointment in almost a century.
Sineenat had breached a code of conduct for courtiers and was “disloyal to the king”, a two-page palace statement said.
Sineenat’s appointment as consort followed the king’s marriage to the deputy head of his personal bodyguard, Suthida Tidjai, 41. He named her his queen, just days before his coronation in May, with the title of Queen Suthida Vajiralongkorn na Ayudhaya.
The statement also described Sineenat as “ungrateful”.
“Royal Noble Consort Sineenat is ungrateful and behaves in ways unbecoming of her title. She is also not content with the title bestowed upon her, doing everything to rise to the level of the queen,” the statement said.