Kingdom of Vientiane
Isan may have had historical leveling processes. The settlement of the region's interior areas led to dialect mixing and the development of transitional areas. The Vientiane dialect also likely had a major role in bringing Isan varieties closer. The provinces of Loei, Nong Khai and Bueang Kan border areas of Laos where Vientiane Lao is spoken, and together with Nong Bua Lamphu and much of Udon Thani, were long settled by Lao speakers of these dialects from the time of Lan Xang as well as the Kingdom of Vientiane. The destruction of Vientiane and the forced movement of almost the entire population of the city and surrounding region after the Lao rebellion greatly increased the population of Isan, with these Lao people settled across the region.