The events were held on the orders of His Majesty King Maha Vajiralongkorn and presided over by Privy Council President Prem Tinsulanonda and the Supreme Patriarch.
Prime Minister Prayut Chan-o-cha, Cabinet members and civil servants also attended the events.
Prem paid respects to the royal portraits of the late King and HM the Queen before Supreme Patriarch His Holiness Somdet Phra Ariyavongsagatayan led 175 Buddhist monks in chanting holy verses.
Another prayer session was held to pay respects to all ancestral kings and the image of Phra Siam Devadhiraj as well as to offer blessings to the Queen.