A reliable, practical method for estimating the evapotranspiration associated with rice cultivation is vital for proper water management in Thailand. We investigated the possibility of estimating rice-related evapotranspiration using only daily air temperature and wind speed, as a practical method for local application in Thailand. By applying regression analysis to a theoretical investigation, we developed a set of daily based equations that estimated evapotranspiration of rice cultivation for a typical Thai plains environment during the rainy season. The estimation error of the developed equations was approximately 20% on a daily scale, and 10% on a weekly scale. Although additional validation of the derived equations is needed for application at other location and at other times of the year, the developed equations show potential for use in water management of cultivation in Thailand.