Using choice experiment, the objective of this study is to estimate international tourists' preferences and willingness to pay for ecofriendly services which related to river and natural environment conservation of hotel industry in Vangvieng, a popular tourist town in Lao PDR. We used the mixed logit to take into account of preference heterogeneity by allowing coefficients to be normally distributed and assumed to vary among individuals. The result shows that all ecofriendly practices offered in this study are significantly preferred by tourists. Income, age, and education did not have significant effect on the probability of choosing ecologically friendly practices of hotel and attributes to support the ecotourism of the area; however, this study provides important information that female tourists are more receptive to a new alternative. These findings do not only support the provision of good and green services in Vangvieng Town, but will also be useful for policy maker to enhance the sustainability of ecotourism in Laos.