This paper describes the development of an automated system to monitor total suspended solids (TSS) in the main channel of the Mae Sa River in northern Thailand. Logged discharge (Q) and turbidity (NTU) values were compared with hand-sampled TSS concentrations that were determined during six runoff events (n = 85 samples) and 13 other baseflow periods. Measured TSS values ranged from 10 to 7600 mg L-1, reflecting variable conditions between dry-season baseflow and wet-season stormflow. Because of hysteresis effects in the TSS versus discharge relationship, and high sediment concentrations that surpass the detection limits of the turbidity sensor during some storms, TSS was predicted best using multiple regression with both Q and NTU as independent variables. The estimated annual TSS load for 2006 is about 79 822 t, which is equivalent to a basin yield of 1076 t km-2 for the 74-km2 catchment.