New overseas retail formats have been entering emerging markets since the late 1990s. Accordingly, research on the advance of transnational retailers into emerging markets has recently flourished, and Thailand, one of the most popular host countries for transnational retailers, has often been examined as a case study. Many of these studies clarify the retail internationalization process and conclude that the new formats are driving the host countries' traditional distribution system toward a fundamental change. Although these studies consider the host countries' circumstances, they do not necessarily pay sufficient attention to specific characteristics of those host countries. In case studies of Thailand, the specific roles of intermediaries throughout the entire retail and distribution system are commonly overlooked. This paper argues that intermediaries continue to play an important role in Thailand's distribution systems, especially in the system of fresh vegetable distribution. This study first explains why earlier studies often attached less importance to the examination of intermediate distribution systems, despite the necessity of considering the roles of intermediaries for a deeper understanding of the impact of new retail formats on the host countries' distribution system as a whole. After discussing the key roles of intermediaries in Thailand's vegetable distribution system, this paper concludes that because modern retailers' involvement, particularly that of transnational retailers, at the agricultural production stage is still limited in Thailand, they often rely on intermediate distributors, such as local assembling wholesalers, coordinator-type intermediaries, and wholesale markets, for the intermediate distribution process.