This research examines marriage or “Et Pa Su” of the Phu Tai in Na Do Village, Tambon Na Sok, Muang District, Mukdahan Province. It was found that changes in marriage patterns had affected their identity. Research revealed nine characteristicss of ethnic marriages as follows.
          1.Dress. In the past, brides and grooms were dressed in traditional costumes, whereas today they are dressed in modern costumes.
          2.Language. In the past, different forms of ethnic poetic language were used during the proposal, however, these forms of language are currently used less frequently.
          3.Differences between male and female roles. Phu Tai is a patriarchal society. Currently, men and women appear to be equal, however, females are still obliged to show respect to males as customary in the past.
          4.Beliefs in supernatural power or prototype
          5.Showing respect to senior members and siblings as well as to relatives are still important.
          6.Humbleness as well as respect to others
          7.Gratitude by showing appreciation to one another
          8.Good relationships
          9.Collective unity of community members

          These characteristics are becoming less important and are subject to socially accepted norms. Additionally, new marriage characteristics are being shaped as a result of interaction with others.
          There are a number of factors affecting changes in marriage characteristics, including changes in economy, community, society, occupation, income, education, social status of individuals, cross-marriage, and cultural diffusion. These factors have affected the process of marriage with new steps being added, while traditional ones are being culminated.
          To reduce marriage expenditure, it was found that community power, existing identities and values should be used to motivate community members to reduce related expenses. Those expenses that could be reduced might include items related to welcoming guests, food , drinks, dress rent, makeup, invitation cards, and entertainment (electronic music).