King Ramathibodi's position was likely secured by political marriage and family ties. He was married to a daughter of the ruling family of the Kingdom of Suphanburi, and may have also married into an alliance with the rulers of Lopburi - it was likely the king of Lopburi that he was initially chosen to succeed. He appointed both his brother-in-law and son to positions of leadership in Suphanburi and Lopburi, respectively, and established his own capital in the new city of Ayutthaya. King Ramathabodi's reign bound together the Khmer rulers of Lopburi, the Tai in the west, and the Chinese, Javanese, Bugis and Acehnese merchants who inhabited the coastal areas.
According to a better-known source, a seventeenth-century account by Dutchman Jeremias Van Vliet, a 'renowned legend' stated that Ramatibodi was an ethnic Chinese, having sailed down from China. After succeeding in trade, he became influential enough to rule the city of Phetchaburi, a coastal town of the Gulf of Thailand, before travelling up to Ayutthaya.
King Ramathibodi's death sparked a conflict over succession. Initially, his son King Ramesuan became ruler of Ayutthaya, but King Ramesuan later abdicated in favor of King Ramathibodi's brother-in-law, King Borommaracha I. Some sources indicate that the abdication occurred peacefully, while others indicate that King Ramesuan's abdication followed a bloody civil war.