This research explored the implementation of local wisdom of Karen, Lavua, and Thais for conserving the forest ecological system in northern Thailand with a focus on the methods of the Karen comparing them with those of Lavua and Thais. Subsequently, the success of the implementation was analyzed. The research findings revealed that the villagers perceived the forest ecological system as comprising both animate and inanimate entities, such as, animals, plants, human beings, earth, water, minerals, rain and the temperature. The villagers based their production systems and livelihoods on forests by adhering to the principles of conservation, interdependence, respect, fear and gratitude. The forest ecological system began to disappear, when there was a development of production factors and a commercial production system. However, some villagers had still maintained the ecosystem through rituals related to forest conservation, such as, animistic beliefs and practices, a wier system, mountain irrigation, tree ordination, river conservation rituals, reforestation, crop rotation, and construction of fire breakers. These practices expressed respect, gratitude, fear, imploring, and generosity between man and man, and between man and supernatural entities. At the time of the study, there were approximately 400 patches of forest land, where villagers collectively helped conserve and 42 forest conservation organizations formed by villagers in the Ping, Wang, Yom, Nan, Kok, Ing, Yuam and Pai River Basins to help with the conservation initiatives. Forest conservation problems included encroachment by politicians and investors with the collaboration of some groups of villagers. Furthermore, officials from some state agencies did not accept conservation methods of the villagers, trying to relocate them from forest areas, where they had long inhabited. The researcher suggested some solutions to solve these problems by implementing religious and cultural principles to create intellectual immunity against consumerism and materialism while leading their lives in accordance with the nature. Additionally, structural problems had to be resolved, including political, legal, economic and educational systems based on sustainable and interdependent co-habitation between plants, animals and human beings in the same ecological system (pp. (1)-(2)).