The work investigates knowledge and logical processes about diseases and bad luck in the ethnic Lisu in northern Thailand, based on the Competence and Data Input Framework in conjunction with cultural interpretation so as to explain the relationship between sickness and supernatural power or between sickness and shamans, as well as their thinking system, beliefs and awareness of reality that affect their psychological process through their cognitive ability in order to understand their performance. According to their perception, causes of sickness and bad luck could be both natural and supernatural diseases. Thus the logic of polarities would help explain their social and political structures that result in the contexts of finding causes for sickness and curing.