Vacharaesorn Vivacharawongse, the second son of His Majesty the King, is on a visit to Thailand after 27 years living abroad, to the delight of many Thai people.
A 30-second video of Vacharaesorn, 42, walking out of the arrival terminal at Suvarnabhumi international airport went viral on social media on Monday.
He was seen waving to a group of Thais who were there to greet him. He gave them a wai, smiling and saying, "Thank you very much", before proceeding to an exit.
Vacharaesorn reportedly departed from the John F Kennedy airport in the United States on Aug 5 on board a Cathay Pacific flight to Hong Kong, where he took a connecting flight that landed at Suvarnabhumi on Sunday evening.
From the airport, he went to a hotel in the heart of Bangkok. It was reported he would stay in the country for about one week.
No announcement of his visit was made by the Royal Household Bureau.
On Monday morning, Vacharaesorn went to Wat Ratchabophit Sathitmahasimaram Ratchaworawihan in Phra Nakhon district where he paid respect to the Supreme Patriarch.
He then proceeded to pay homage to the City Pillar before moving on to Wat Phra Si Rattana Satsadaram (also known as Wat Phra Kaew, Temple of the Emerald Buddha) and Wat Hong Rattanaram Ratchaworawihan temples where he posed for pictures at the request of people who happened to recognise him.
Vacharaesorn is second of the four sons of HM the King and his former consort Sujarinee Vivacharawongse. Their younger sister is Her Royal Highness Princess Sirivannavari Nariratana Rajakanya, who lives in Thailand.
The four brothers had their primary education in Thailand before moving to the United States.
Vacharaesorn has both bachelor's and master's degrees in law from Stetson University College of Law in the United States. He is a legal counsellor at a law firm in New York, where he has lived for 27 years. He has reportedly joined other Thai people in the US in activities showing Thai traditions and culture.