They were accompanied by Her Royal Highness Princess Bajrakitiyabha, Her Royal Highness Princess Sirivannavari Nariratana, and His Royal Highness Prince Dipangkorn Rasmijoti at the ceremony held in the Amarin Winitchai Throne Hall.
During the ceremony, the King attended prayers by a group of Buddhist monks, after which he offered alms to them.
He paid respects to royal urns carrying the relics and ashes of former Thai kings of the Chakri Dynasty. He also sprinkled holy water on the urns, as part of a Songkran tradition.
The Queen offered robes to the monks who participated in the ceremony.
Their Majesties then paid respects to the nine Buddha images built in honour of the past nine monarchs of the Chakri Dynasty — Kings Rama I to Rama IX.
They later paid homage to the royal urns of the former kings on their way out of the throne hall.
Before leaving the Grand Palace, Their Majesties greeted a large group of people gathering for royal audience.
Members of the public were allowed to pay homage to former kings at Prasat Phra Thep Bidon (Royal Pantheon) in the Emerald Buddha Temple, inside the Grand Palace complex, from 8am to 1pm on Friday.