This action research applied a means-end theory as a frame to explore customer's preference on product attributes, benefits and value that drive purchasing decision in order to utilize the market information in design development of new products to meet customer expectation. A case study of a new fashion design T-shirt brand namely "COMMON-T" by local Thai designer was selected. Style, design, price, and brand name are found as preferred attributes that lead to purchasing decision. Mix & Matchable feature, uniqueness, cost-worthiness, and being Thai brand are perceived as benefits that serve customers' value of satisfaction, belongingness, and self fulfillment. Understanding these customers' insight, afterward the designer attempts to emphasize on building a brand identity and offer the most-up-to-date trend T-shirt at an affordable price. Positioning itself as the Thai designer brand whose products offer global standard quality is not only allows COMMON-T to differentiate itself from counterfeiters, but also a key to accomplishment.