The research entitled Cotton Dyeing With Mekong Basin Soil for Application in Costume Design aimed to 1) study the soil chemical properties, physical properties, ratio, dyeing duration, and durability of the colors on cotton dyed with Mekong Basin soil, 2) apply the cotton dyed with Mekong Basin soil in costume design. The research is a mixed method research consisting of experimental research and quantitative research. The data was collected through records of experiment results, surveys, interviews, and questionnaires. The data was analyzed using Pore Model and Adoption and Innovation theory. The research results show that the Mekong Basin soil has the highest aluminum value of 9811.000 mg and is categorized as sand, with the following composition: sand 39.40 percent, silt 47.05 percent, and clay 13.55 percent. When used for dyeing cotton, it was found that the different concentrated ratio and the dyeing duration does not affect the durability of color when washed, sweat resistance, and abrasion resistance. Overall, the test result shows a level of 2-3 or more, which is acceptable according to Thai Community Product Standard 18/2557. On applying the cotton dyed with the Mekong Basin soil for costume design, it was found that naturally dyed costumes are often found in medium-priced markets, including men's and women's costumes. The opinions of consumers are at the highest level, with an average of 4.52, with a standard deviation of 0.61. The research entitled Cotton Dyeing With Mekong Basin Soil for Application in Costume Design can be further developed for business using the ratio of natural dye with soil to processed products and export at the international level.