South of Muang Sing it appears that there were considerable population movements taking place from the 16th to the 19th century as well, in both the Nam Tha Valley and Vieng Phoukha. In 1587 a group of 17 Tai-Yuan families arrived in the Nam Tha Valley from Chiang Saen, settling near present-day Vieng Tai Village.
By 1624 Muang Houa Tha was established under the traditional Tai Muang administrative structure, ruled by 4 nobles of the Saenhansulin family. In 1628, Pathat Phoum Phouk and Pathat Phasat were constructed as symbols of friendship and neutrality between Muang Houa Tha and Chiang Saen. The original Pathat Phoum Phouk still exists and is located south of Luang Namtha Township. The ruins of Pathat Prasat, on the other hand, are north of town near the source of the Nam Dee Stream but have almost completely disappeared.