Results: From the line transect method, we found the prevalence of water monitors is increasing every year. The water monitor distribution was concentrated along the water sources in the Kasetsart University, Bangkhen campus, The population size and density increased during every year of the study. The area where the most water monitors were found was the lotus pond next to the main auditorium, as well as Sam Buraphachan Monument area and the men's dormitory area. From the two survey methods it was found that the area where water monitor were not found present was the pond area behind the Chulabhorn Swimming Pool and the Kasetsart University Laboratory Center for Educational Research and Development.