On 1 October 2018 in Melaka, Malaysia, the 24th Indonesia–Malaysia–Thailand Growth Triangle (IMT-GT) Ministerial Meeting directed a review of existing IMT-GT economic corridors (ECs), and a study of the proposed sixth corridor linking Pattani–Yala–Narathiwat in Thailand with Perak and Kelantan in Malaysia, and with southern Sumatera in Indonesia. The countries requested technical assistance from the Asian Development Bank (ADB) in conducting this review.1 The economic corridor approach to development was first emphasized in the IMT-GT Road Map 2007–2011 as a key anchor for clustering major economic activities in the subregion. The IMT-GT Implementation Blueprint 2012–2016—the successor to the road map—included economic corridor development programs and projects among the flagship initiatives in the transport and energy sector. The importance of economic corridors was carried over to the Implementation Blueprint 2017–2021, which reaffirmed economic corridor development as a spatial framework to help achieve the IMT-GT 2036 Vision.