The third emigration from ‘Muang Wang Aang Kum’ to basin of Mekong river is mainly caused by usurpation of Tai. If any of them is not their back-up, one would expect to be killed. Because of this, Thai King allowed them to settle down in Baan-Bung-Waan (Muang re-nu as of now). In addition to the first main reason, at that moment there is a news spread on the fact that Mekong river area is abundant with foods and no widespread disease. Therefore, Tao-Sai is the leader in encouraging and bringing people from the left of Mekong river, which is Laos to the right of Mekong river, which is Thailand. Due to this conflict, Chao Anuwong demand to be independent from Thailand by declaration of war. This is the creation of Thai-Laos war in Buddhist era 2369 to 2371. Thai army move the troop by going against Laos for its rebel. Laos later lost to Thailand, which Laos force to move their people to Thailand. At that moment, Phraya Rajsuphawadee( Sing Singhaseni), army leader, didn’t destroy Viangchan, according to command of the King Rama III but appoint Viangchun’s leader to continuing control the city. King Rama III later found out this fact, and therefore, he was very frustrated. In this same year, he then commanded him again to declare the war. Chao Anuwong contrive up the plan for Vietnamese to to surround Viangchun, which allowed Thai troops entered Vianchun easier. This led to demolition of the city. As a result, Laos people cant live in Viangchun anymore, people were therefore, have no choice but to move to Thailand.