The aim of this research studywas to examine the evolution of the costumes of the Tai Tang groupfor design and developmental purposes in order to use costumes for the creation of new products in Bolikhamxay Province, Laos PDR through a qualitative research process. The tools used in this research were surveys, observations, interviews, and group discussionswith identifying populations and samples. The data was analyzed utilizing theories and concepts of Cultural Ecology and Product Design and was presented using descriptive analysis. The research results showed that the evolution of the costumes of the Tai Tang in BolikhamxayProvince beganduring the historical period and has been passed downthrough the generations. The evolutionary processes can be dividedinto six areas.Firstly, there isthe evolution of the patterns of thecostumes from the past, which were woven and worn in their daily lives. However, at present, these costumes are mostlyused in their rituals. Furthermore, the patterns of the textiles have been influenced bynature and the natural environment. Secondly, regarding the evolution of the materials used in the costumes, the concept has been concerned with the use of natural materials from the past until the present. Currently, some natural materials have becomerare at their sites, so they must survey or import materials from other sites. Thirdly, there has been an evolution in the costume design process. In the past, the production process focused solely on human resources to make handcrafts, but that was a lengthy process.Currently, they arepurchasing some raw materials from sites nearby and are using some machinery in their production processes. Fourthly, with respect to the evolution of theaesthetics of the Tai Tang costumes,the artistic compositionsrepresented characteristics,such as unity in the past, which was related to patterns, which were balanced on the left and right sides.