King Rama I, the first monarch of the Chakri dynasty, established the Rattanakosin Kingdom after moving the capital from Thonburi to Bangkok on April 21, 1782.
The shrine and pillar, also known as lak muang, was erected at the time to mark the city’s founding in what is now Phra Nakhon district.
Accompanying Prayut at Friday’s ceremony were acting Deputy Defence Minister General Chaichan Changmongkol and Defence Permanent Secretary General Sanitchanok Sangkhachan.
The PM paid homage to the city pillar and other sacred items around the shrine, including the Buddha image.
The religious ceremony was conducted by nine monks led by Somdet Phra Maha Weerawong, secretary of the Supreme Patriarch.
Prayut told reporters covering the ceremony that he had wished for a peaceful Thailand.
Asked why he had a sullen face during the ceremony, Prayut said it was because of the heat. The PM insisted his glum look had nothing to do with the unexpected appearance of whistleblower Chuwit Kamolvisit during his election campaign in Chinatown on Thursday.
The former soapy massage tycoon and politician showed up on Yaowarat Road to protest cannabis legalisation and confront Prayut.
The prime minister was eating noodles at the time but made a hasty retreat after Chuwit interrupted his meal.