Sunthorn Phu was born in the reign of King Rama I, on June 26, 1786. His family's house was located behind the royal palace, near the location of present day Bangkok Noi train station. His father was from Klaeng District in Rayong province.
At the time the poet was born, Bangkok had been established as the Thai capital just four years earlier, founding the Rattanakosin era which continues to the present day.
His father and mother divorced, with his father becoming a monk at Bangrum temple; and his mother becoming a wet nurse for the Royal family. Phu had an opportunity to work in the palace with his mother, where he eventually fell in love with a lady in the palace named Jun, who was related to the Royal family. The couple were arrested and punished because their relationship violated the traditional social order, but they were pardoned on the king's death.
Phu later returned to Rayong to visit his father, and wrote a poem about the journey called “Nirat Muang Grang" which became one of his most famous poems. He wrote the poem for his fiancé, Jun. After he returned to the palace in Bangkok he married Jun, and they had a son named Pat. It was at this time that King Rama II appointed him court poet. However, the couple were not married long, divorcing after Phu had an affair with another woman. This was the first of many marriages ending in divorce, although he later professed that the wife he had loved the most was Jun. Phu became an alcoholic, and, around 1821, was jailed after a fight.