This paper is a conceptual study that attempts to analyse the possible effects of the development of the Kra Isthmus Canal on ASEAN relations. The Kra Canal would constitute a mega-project, a passageway that would connect the Andaman Sea and the Gulf of Thailand at the Isthmus of Kra, Thailand. Although the proposed Kra Canal is projected to provide many economic and trade benefits to Thailand, and to the region as a whole, steps toward its development have yet to be taken. There has been much debate over the costs for trade, the costs for the environment, national and regional security concerns, as well as major concerns related to political and economic relations in the region. Therefore, one of the main purposes of this study is to contribute to the debate on the possible impact of the devel-opment of the Kra Canal on ASEAN’s regional relations. In particular, it proposes that the development of the Kra Canal could threaten regional solidarity as it would physically divide maritime Southeast Asia from main-land Southeast Asia, which would ultimately result in an economic, cultural and political divide of ASEAN itself.