Chairacha appointed his brother Prince Thianracha (later Maha Chakkrapat) as the Uparaja but did not grant him the title of King of Sukhothai as Chairacha was trying to unite the two kingdoms by reducing the power of Sukhothai nobles.
Chairacha chose to appoint his brother as the Uparaja, a position with significant power, but did not bestow upon him the title of King of Sukhothai. This was part of Chairacha's strategy to consolidate power and diminish the influence of Sukhothai nobles in order to unite the two kingdoms.