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To understand the geological control and tectonic forcing on the development of a major river system in SE Asia, new detrital zircon U-Pb and Hf isotopic data from the Salween drainage, Myanmar is reported. Three samples with a range of deposition ages corresponding to different tectonic periods of the Sibumasu Terrane reveal a dramatic change in the drainage system. Differing from the detrital compositions of modern sediments from the Salween river mouth, a Late Triassic sandstone sample shows zircon age distribution implying that the Salween drainage may have been connected at that time to the northeastern part of the Songpan-Ganzi Terrane and western part of the South China Block. U-Pb ages and ɛHf(T) isotopic data of detrital zircons from other major rivers in SE Asia, including the Yangtze, Red, and Mekong Rivers in the east and the Irrawaddy River and the Yalu-Tsangpo in the west are further synthesized. A marked discrepancy in zircons younger than Jurassic ages is identified. Similar to results from the Salween samples, these young zircons from the eastern rivers are overwhelmed by an old, recycled crustal component exhibiting negative ɛHf(T) values. In contrast, those from the western rivers are dominated by juvenile components that are characterized by high and positive ɛHf(T) values. The Salween drainage, therefore, lies in the frontier with its western outline broadly depicting the boundary between mature and juvenile crustal provinces in SE Asia.