This work examined the historical background of the Thue Ti ritual of the Hmong at Mae Sa Mai village in Tambon Pong Yaeng, Mae Rim district, Chiang Mai province, which is located in the Suthep-Pui National Park. The community had originally migrated from Myanmar, migrated back to Myanmar and then migrated back to the community in Thailand again. The purpose of this ritual is due to the Thue Ti Deity or the Earth Deity to protect their crops, animals and community members from natural disasters and negative actions from people. However, the belief in the ritual has changed through time. For instance, after WWII, the Hmong received guns from Japanese soldiers, making them less afraid of wild animals than before. They converted to Buddhism as well as Christianity, and were involved in cultivating commercial crops in place of opium, decreasing the role of the ritual. Presently, the villagers have adjusted the ritual to suit the changing trends in order to conserve forest resources and watershed areas.