This study focuses on the environmental planning for Thai National Parks. A qualitative approach with depth interviews was carried out among stakeholders, including local residents, national park officials, and vendors. The results indicated that systematic planning must be developed in order to provide a flexible and complete plan to cope with the fast-changing and demanding environments of the national parks when the tourism industry of Thailand has been growing rapidly with a greater variety of visitors from around the world. The readiness and the adequate number of the national park officials must be improved to keep up with these new challenges. The impact of tourism development on the environment can be at the critical level if the effective environmental plan is not implemented. Directions for future research and recommendations are also provided.