He spent most of his early years as a prince of the royal house in exile at Huế (now in Vietnam).
His father Prince Som Phou fled to Vietnam upon the placement by the nobles of his younger brother (Setthathirath II's uncle) Suliyavongsa was king of Lan Xang.
Upon the 1694 death of King Suliyavongsa, a noble named Tian Thala ascended to the throne.
Setthathirath II then sent his brother to take the northern city of Loung Prabang from his cousin Prince Kitsarat (or Kitsarath), a grandson of King Suliyavongsa, who refused to recognize his authority.
In 1713, another grandson of Suliyavongsa, Prince Nokasat Song or Nokasad, saw the opportunity to break away from Lan Xang to the South, and was also granted independence from Siam to form the Kingdom of Champasak, which further divided the Lao Kingdom.