This research aims to investigate volume, heat, and freshwater transports in the Gulf of Thailand for each season. The Model grid used in this research is the orthogonal curvilinear grid which is constructed via cubic splines and solving Laplace's equation. For the vertical grid, the sigma coordinate is introduced to deal with significant topographical variability. The data used for calculating the volume, heat, and freshwater transports consist of bottom topography, current velocities, potential temperature, salinity, and seawater density, and are calculated from the primitive equations. A numerical method used to solve the primitive equations is the finite difference method. The results show that the highest and lowest values of volume, heat, and freshwater transports in each season occur at the same region, and the direction of volume and heat transports are all same in the Gulf of Thailand, but the freshwater transport is the opposite direction of volume and heat transports. The highest values of volume, heat, and freshwater transports occur between latitudes 7°N to 8°N in the winter and at the connection section between the Gulf of Thailand and the South China Sea in the summer, rainy season, and the end of the rainy season. Their lowest values occur at latitude 11°N in the winter, between latitudes 8°N to 9°N in the summer, and between latitudes 10°N to 11°N in the rainy season and the end of the rainy season. In order to validate the results, a comparison was made with the results of Wyrtki's research which investigated the volume transports of Southeast Asian Waters. In a comparison of the results, it can be summarized that the results of our research are on track.