A study of the Shan rebellion which broke out in the northern Siamese town of Phrae in July 1902 and continued until May 1904 serves as the basis for an exploration of the interaction between sedition and state-making in the Mekong borderlands at the turn of the twentieth century. French archival material makes clear that the rebellion was not just a two-dimensional struggle between discontented Shan and the expanding Siamese state, as it has been commonly understood. Rather, the rebellion was a multifaceted encounter with competing processes of state-making in the borderlands of Siam, Burma and French Indochina. The French sources show how the Shan rebels attempted to mobilize precolonial political alliances that extended well beyond the boundaries of Siam. They also show how the rebellion intersected productively with the recently established border between Siam and French Indochina. Modern borders are often portrayed as constraining the lives of borderlanders, but this marker of modern state power provided the rebellious Shan with sites of strategic refuge and tactical manoeuvre. Sedition and state-making were closely intertwined.