The study assessed the variations of surface water quality in Soc Trang province, Vietnam using national technical regulations on surface water quality (QCVN 08-MT:2015/BTNMT, column B1) and water quality index (WQI), cluster analysis (CA), principal components analysis (PCA), discriminant analysis (DA), and correlation analysis. The results showed that the surface water was contaminated with organic matters and microorganisms. CA divided the monitoring months into three clusters representing dry season, transitional period, and rainy season, leading to a reduction of 75% monitoring cost. Correlation analysis showed turbidity, total suspended solids, organic matters, nitrogenous and phosphorus compounds, coliform were interrelated. The WQI indicated that the water quality ranged from poor to good. PCA showed five main factors explaing 88.8% of the variations in water quality. The surface water pollution sources were from domestic wastewater, wastewater from production activities, saltwater intrusion and stormwater runoff. Total organic carbon, total suspended solids, coliform, dissolved oxygen, temperature, pH, electrical conductivity, chloride, sulfate and chemical oxygen demand resulted in difference in water quality between seasons. The current findings provide important scientific information for the use and better management of surface water quality in the study area.