This research study is purpose , 1) To study the principle of trifold base of meritorious action in scriptures of Buddhism., 2) To study the trifold base of meritorious action which found in fourth month festival. 3) To study the way of lives of the people in Nakhai sub-district , Tansum district , Ubon Ratchathani province which connected in principle of trifold base of meritorious action that found in     fourth month festival.  

Methodology  for research is used the documentary and field research studies, this research studies found that,

      Meritorious action is the root of ethical teaching in Buddhism, it is principle for promote the virtuous life to individual and public affair; books of Buddhism categorized it to three parts at 1). Danamaya (offering) is meritorious action consisting in giving, 2), Silamaya (moral) is the meritorious action consisting in observing the precepts and 3). Bhavanamaya (cultivate) is the meritorious action consisting in mental development.  It differentiated by its quality and benefits according to the its virtuous position as the quality of moral is more beneficial action than offering , and mental development is super.

               Fourth month festival is a part of 12 months tradition or Heet and also stated it that Bon Prahvet (merit in Pravesantara Jataka) , it has been being in Northern part of Thailand for long time, all steps of activities and chapters is followed by trifold base of meritorious action such as offering, morality and mind cultivation.

               The way of lives of the people in Nakhai sub-district , Tansum district , Ubon Ratchathani province is followed the principle of trifold base of meritorious action such as offering, morality and mental development which found in the fourth month festival or Prahvet  and also influenced on the philosophical life through the culture, literature, moral painting, tourism, socio – capitalism , virtuous life , solidarity, and social work.