The objectives of this thesis are: to study the Uposathasila in Theravada Buddhism, to study the method of Uposathasila observing of the people in Bannonmueang, and to analyse the result of Uposatha observing in developing the quality of life. However, this thesis is conducted based on documentary research, field work approaches, and critical analysis.

                  The result of the study found that Uposathasila was an intention to observe moral rules in Buddhist holy days. It was the Buddhist practice of preventing oneself from transgressing the Eight precepts during one day and one night. This also was considered as the noble practice for the lay Buddhists.

                  This study also found that most of the people in Bannonmueang had no clear understanding about the practice of Uposathasila observing. However, rather practiced by themselve in the houses, they likely to came to the temple, and observed Uposathasila in the Buddhist holy days; because, to them, in the temple they could did more meritorious actions such as Dhamma listening, offering, practicing insight meditation…ect.

                  Neverthelesss, this study also found that the result of Uposathasila observing of the people in Bannonmueang helped a lot in developing the quality of their lives. For instance, they became healthier, reduced an outcome of the family in drinking and self-decorating, and it was an alternative means to eliminate negative mental formation. Moreover, they became mindful and had positive view in living and ready to dedicate themselves for the benefit of the country.