By the time of the reign of the 29th Tsampo Tabonyexi, the Sheboye Tribe of Yarlung had fundamentally united the northern and southern banks of the Yarlung Zangbo River, and further outward expansion began. At that time, there had been two tribal unions along the Lhasa River: Yanbochasung (in the area of Pengbo) and Gyinorjam'en. Tubo Historical Documents of the Dunhuang Edition recounts their conflicts:

Senbo Gyidargyawo, the King of Yanbochasung, was a cruel and fatuous ruler who aroused the popular resentment of his ministers and officers. Nyangyisungnabo, King Senbo Gyidargya's family aide, made efforts to offer some advice for better royal administration, but unfortunately, the king not only rebuked him for his advice, but also evicted him from the ministerial ranks. Then, Nyangyisungnabo turned to Senbo Gyichibamsung, the King of Gyinorjam'en. When war occurred, Senbo Gyidargyawo was killed and the Gyinorjam'en tribe annexed Yanbochasung. In recognition of the outstanding service Nyangyisungnabo has performed, King Senbo Gyichibamsung bestowed on him some of the lands that had formerly belonged to King Senbo Gyidargyawo. However, Nyamcenku, who was part of the administration run by Nyangyisungnabo, appealed to the King against the land grant decision, only to be denounced for his action. On the other side, the financial officer Weixuedorikugu was locked in an incessant struggle with the Prime Minster Shenchiretunkon, eventually killing him. The dead man's younger brother, Weiyice appealed to King Senbo Gyichibamsung that Weixuedorikugu should also lose his life, but this, too, was rejected. As a result, Nyamcenku and Weiyice, with their relatives Nong and Caibam joining them later, secretly schemed to pledge alliance to the Sheboye tribe to overthrow King Senbo Gyichibamsung. They sent a trusted aide to Qoingyel to contact Tabonyeshe, who agreed with their plan, even though the king was his brother-in-law. On the eve of the proposed attack, Tabonyeshe passed away and he was succeeded by his son, Luntsan, who continued the war plan. He sent over 10,000 soldiers to cross the Yarlung Zangbo River and took control of the areas along the Lhasa River. Finally, with the cooperation of Nyam, Wei, Nong and Caibam, Luntsan defeated the tribal unions of Gyinorjam'en. From then on, he was respectfully called King Namri Luntsan, and he responded by rewarding his followers for their deeds. Nyam, Wei, Nong were given 1, 500 households as their subjects along with the relative lands, and Caibam was granted 300 households as his subjects. Thereafter, struggles broke out in another small tribal union called Nyamrochekar in the Xigaze area. Minister Qoibosuze killed his king and presented King Namri Luntsan with 20, 000 households and the lands of the Xigaze area, and the king rewarded him according to his outstanding service. From then on, the tribal union of Sheboye united the middle and lower reaches of the Yarlung Zangbo River, the main agricultural area of Tibet.