As recently as 1875 Thailand had an extremely decentralized political system in which regional and local authorities enjoyed considerable autonomy from the central government. By the end of King Chulalongkon‘s reign in 1910, however, a very centralized political system had emerged in Thailand. This rather remarkable transformation from decentralization to centralization has usually been explained in terms of Western diplomatic and economic pressure upon the Thai government in the nineteenth and early twentieth centuries, and the reforms which the government undertook to meet this pressure. Earlier studies by scholars such as Walter Vella, D. G. E. Hall, and John F. Cady have strongly emphasized the importance of Western pressure and advisers for the transformation of the Thai political system. More recent studies, in particular those of David Wyatt, have emphasized the importance of domestic factors in this process of change and stressed the creativity of the Thai response to the West. All of these studies have in common, however, an emphasis upon the importance of national level politics in the process of centralization. It will be the argument of this paper that it is also necessary to examine provincial-level politics in the period from 1875 to 1910 to understand why centralization in Thailand was so thoroughgoing and why it proceeded so rapidly. For this purpose the paper will focus on northern Thailand in the area which is now covered by the provinces of Chiang Mai, Lamphun, Lampang, Phrae, and Nan.