Grand Chamberlain Khwankeo Vajarodaya died at the age of 89 early on Saturday.
Prof Dr Prasit Watanapa, dean of Siriraj Hospital's Faculty of Medicine, said Khwankeo died of coronary artery disease at 4.48am after being treated by medication at the hospital for a while.
His relatives and the Bureau of the Royal Household will move the body to Wat Benchamabophit, where a bathing rite with royally bestowed water will be held at 5.30pm on Sunday.
Palakorn Suwannarat will be the royal representative at the bathing rite, after which a chanting ceremony will be held at 7pm.
Khwankeo was born on Sept 3, 1928 to Phraya Anurak Ratchamontien (Gaad Vajarodaya) and Thanpuying Pua Anurakratchamontien. He was a nephew of Queen Indrasakdisachi and First Consort Phra Sucharit Suda of King Rama VI.
Khwankeo was married to Maj Gen Dr Thanpuying Wattana Vajarodaya in the first royally granted wedding of King Bhumibhol Adulyadej's reign.
He has two sons -- Mr Thaanit, special expert of the Office of His Majesty's Principal Private Secretary, and Mr Dissathorn, a high-ranking executive of the Bureau of the Royal Household.
Khwankeo had a twin brother, Keokhwan, Lord Chamberlain until his death on Sept 15, 2016. He was succeeded by Chirayu Israngkul na Ayudhya.
Khwankeo was the author of The Evolution and Art of Setting Tables, Catering, Beverages and Menus published by Amarin Printing and Publishing Plc in 2002.