This article uses primarily British colonial documents and Singapore sources to examine the history of proposals for the construction of a shipping canal through Thailand's Kra Isthmus from the 1850s. It provides historical background for continuing interest in constructing a Kra canal with the most recent speculative discussions involving Chinese interests. Since the 1850s the idea of a canal was revived on numerous occasions with several detailed surveys conducted over this time to assess the feasibility of a shipping canal via the Kra Isthmus. This research examines how speculation and actual proposals were handled by the British colonial authorities and how this related to the British policy of using Siam/Thailand as a buffer state separating their colonies and those of their European rival France. In colonial Singapore canal proposals created great angst and to some extent this has continued to be the case to the present day. The article suggests that while British colonial policy was always against, or at least not in favour of, the construction of a canal, other factors are equally important for explaining why canal proposals never proceeded beyond planning and surveys.