Fa Ngum
Vientiane remained independent and powerful, and the growing power of Ayutthaya threatened regional stability. In 1356 Fa Ngum marched south to take Vientiane for failing to support his earlier advance on Muang Sua. In 1357 he took Vientiane and the surrounding plains, and marched south to assert Lao control over the areas seized by Ayutthaya. Fa Ngum moved across the Khorat Plateau taking the major cities along the Mun and Chi Rivers and moving as far south as Roi Et.