This work presents the state of knowledge on the endangered and threatened species of Thailand. Its pragmatic purpose is to improve Thailand’s future by providing access to technical guidance for planning development projects or other land-use changes. This information also should stimulate naturalists, professional biologists, or anyone who wishes to learn about the status of animals in Thailand. Which species are now on the brink of extinction from Thailand, and why? How can the Thai people reorganize themselves to reverse the course of destruction? Can ways be found for both the people and the rest of the fauna to prosper? Another purpose is to present a case study of the effects of longterm development for human use on the biological diversity of a tropical country.