The Prince and Princess of Wales will join the King and Queen in granting Royal Warrants — a sort of "seal of approval" — on certain goods and services.
Tens of thousands of demonstrators ignored the order. They are calling for the resignation of military-backed Prime Minister Prayuth Chan-ocha and curbs on the monarchy.
Some experts suggest King Maha Vajiralongkorn's firing of his consort may be an additional power move by a monarch who has worked to amass personal authority since he succeeded his father in 2016.
King Bhumibol Adulyadej, who was the world's longest-reigning living monarch when he died last year at the age of 88, will be cremated in an elaborate ceremony in Bangkok today.
The revered King Bhumibol Adulyadej died in October 2016, with his remains lying in state at the royal palace in Bangkok. The ceremony will conclude a year of mourning for the Thai people.
Prince Maha Vajiralongkorn, son of King Bhumibol Adulyadej, and his now ex-wife, Princess Srirasmi, have ended their 13-year marriage, the palace says.