After the death of King Photisararath, the nobles of Lan Xang were divided, a group supported Prince
Tha Heua, another group of nobles led by Phya Vieng, Saen Marong and Kwan Darmpa supported Prince Lanchang who was born from an Ayutthayan princess. Prince Tha Heua and Prince Lanchang began to split the Kingdom up between them, when Prince Settathathirath was still in Chiang Mai. Hearing of the news of his half brothers, King Settathathirath quickly returned to Lan Xang leaving the affairs of Chiang Mai under Queen
Chiraprapha's leadership. Upon returning to Lan Xang to secure the throne after his father's death, Setthathirath brought the sacred images with him. This move was intended to legitimize his sovereign authority over both the Lanna and Lan Xang kingdoms, effectively making the Emerald Buddha the supreme palladium of his unified realm. The Nobles of Lanna felt that Setthathirath had stayed away too long, and sought another descendant of
Mangrai dynasty to take the throne in 1551. They chose a distant relative of Setthathirath, the Shan Prince known as
Mekuti. Settathathirath subdued Prince Tarua in Louang Phrabang, and sent his general Phya Sisatthamatailoke to go fight Prince Lanchang in the town of Kengsah, Prince Lanchang was defeated and fled to
Thakhek, where the local Lord had him arrested and sent to Phya Sisatthama. The nobles that supported Prince Lanchang were executed, but Prince Setthatathirath pardoned Prince Lanchang and appointed him as governor of Seanmuang. Phya Sisatthama was thus made Lord of Viangchan, and given the title Phya Chantaburi, who built Wat Chan and Pia Wat that can be still found in Viangchan today. In 1553 King Setthathirath sent an army to retake Lanna from Mekuti but was defeated. Again in 1555 King Setthathirath sent an army to retake Lanna at the command of Sen Soulintha, and managed to take Chiang Saen. For his success, Sen Soulintha was given the title
Luxai (Victorious) and offered one of his daughters to King Setthathirath. In 1556 Burma, under King Bayinnaung invaded Lanna. King Mekuti of Lanna surrendered Chiang Mai without a fight, but was reinstated as a Burmese vassal under military occupation. In 1560, King Setthathirath formally moved the capital of Lan Xang from Luang Prabang to Viangchan, which would remain the capital over the next two hundred and fifty years. The formal movement of the capital followed an expansive building program which included strengthening city defenses, the construction of a massive formal palace and the
Haw Phra Kaew to house the Emerald Buddha, and major renovations to
That Luang in Viangchan. In Luang Prabang, Wat Xieng Thong was constructed perhaps in compensation for the loss of status as the former capital of Lan Xang, and in
Nakhon Phanom major renovations were made to
That Phanom. ==The Burmese invasions==