Surface water is essential to life, but it is seriously influenced by anthropogenic and natural impacts. Extraction of inside information (for examples sources and key variables influencing water quality) from monitoring data of surface water quality is a crucial task. This study was to intensively evaluate surface water quality in North Vam Nao using Principal Component Analysis (PCA) and Cluster Analysis (CA). The water quality parameters from seven locations during the period 2010–2022 including temperature, pH, total suspended solids (TSS), dissolved oxygen (DO), biological oxygen demand (BOD), chemical oxygen demand (COD), nitrate (NO3−-N), ammonium (NH4+-N), orthophosphate (PO43−-P) and coliforms were collected. The results show that surface water quality is seasonally varied, except for pH. The PCA results predicted the main sources of water pollution were possibly hydrological conditions (rainfall, erosion) and human activities (domestic, agricultural and industrial activities). CA classified the water quality into three clusters for both dry and wet seasons. The common pollutants in both seasons were total suspended solids, organic matters, nutrients, and coliform. All the parameters temperature, pH, TSS, DO, BOD, COD, NH4+-N, NO3−-N, PO43−-P and coliform are key surface water parameters needed to be monitored. The results of the current study could be used for designing surface water monitoring at the study area.