The ceremony took place at 10.39am at the Grand Palace’s Phra Suralai Phiman Hall, Phaisan Thaksin Throne Hall, Phra That Montien Hall and Amarin Winitchai Throne Hall.
During the ceremony, Their Majesties paid respect to sacred objects, including the nine Buddha images built in honour of the nine monarchs of the Chakri Dynasty.
Their Majesties also offered alms to Buddhist monks at the throne hall.
The public was allowed to pay homage to former kings at Prasat Phra Thep Bidon (Royal Pantheon) in the Emerald Buddha Temple inside the Grand Palace complex until 1pm on Sunday.
The Grand Palace is located in Bangkok’s Phra Nakhon district.