Somdet Phrachao Prasatthong () (reigned 1629–1656) was the first king of the Prasat Thong dynasty, the 4th dynasty of the Siamese Ayutthaya kingdom. Accounts vary on the origin of Prasat Thong. While traditional Thai historians hold that he was an illegitimate son of King Ekathotsarot, Jeremias van Vliet's account states that he was the maternal cousin of King Songtham – his father was Okya Sri Thammathirat (), elder brother of the mother of King Songtham. He was born during the reign of King Naresuan around 1600 and was known to cause mischief in the royal court. He ruined the palace Agricultural Initiation Ceremony and was threatened with execution; only pleas from the queen of King Naresuan won a reduction of the punishment to life imprisonment. He was later pardoned and given the title