People nationwide joined in organising activities to mark His Majesty the King Maha Vajiralongkorn Bodindradebayavarangkun's birthday on Friday as world leaders sent messages congratulating him on the special occasion.
Government agencies and Thai embassies around the world held merit-making events. Highlights included visits by top government officials and the armed forces led by Prime Minister Prayut Chan-o-cha and his wife, Naraporn, to the Grand Palace where they wrote well-wishing messages for His Majesty.
Also signing the birthday book for the King were former prime ministers Yingluck Shinawatra and Somchai Wongsawat as well as leading Pheu Thai Party figures.
Russian President Vladimir Putin also sent a message expressing his sincere congratulations on the occasion of the King's 65th birthday.
"I whole-heartedly wish you good health, happiness, well-being, every success and all the best," Mr Putin wrote.
He said Russia highly values friendly relations with Thailand and voiced his confidence in continued bilateral cooperation.
US President Donald Trump and his wife, Melania, also sent birthday greetings to the King and offered His Majesty and the royal family their very best wishes.
He wrote that the friendship between the United States and Thailand spans almost 200 years, dating back to the early days of the Chakri Dynasty when King Rama II first wrote to then president James Monroe.
At noon on Friday, the navy fired a 21-gun salute at the historic Wichai Prasit Fort at the naval headquarters.
Stamp enthusiasts were also treated to newly released stamps honouring His Majesty the King.
They were the first set of commemorative stamps to have been produced and put on sale under the current reign.
Monks collect alms from people at the Royal Plaza. Many people turned up early yesterday to make merit for His Majesty the King's birthday. The event, which was joined by state officials, was also dedicated to the late King Bhumibol Adulyadej and Her Majesty the Queen. Chanat Katanyu
About 700 people queued up outside the Thailand Post head office in Bang Rak district early on Friday to purchase the stamps.
Many stood in line hours before the first queue card was distributed at 8am.
The first 500 stamps had been sold out within half an hour as each person was restricted to buying only one set of 10 stamps, priced at 10 baht apiece.
Privy Council president Gen Prem Tinsulanonda and privy councillors were on hand to congratulate a group of volunteers formed under His Majesty's initiative in a clean-up operation of the residential communities in Klong San district.
The event was also attended by the armed force commanders, the Bangkok governor and the interior permanent secretary.
Air Marshal Pakdee Saengchuto, deputy private secretary to the King, said His Majesty wanted the volunteer group to be a unit combining the efforts of individuals in government agencies, the private sector and the general public in developing their own communities.
Similar units will be extended to all regions of the country as they stand ready to deliver assistance in emergencies and mitigate disasters.
Morning alms were offered to monks at mass gatherings of people and state officials in many provinces, including Yala, Sa Kaeo, Phitsanulok and Ang Thong.