The Indochinese spitting cobra, Naja siamensis Laurenti, 1768, is redescribed. In order to avoid future confusion with other Asiatic Naja species, and to fix this scientific name irrefutably, we designate a neotype for this species, and designate the same specimen as neotype for the junior synonym Naja naja isanensis Nutaphand, 1982. The pattern of geographic variation in this species is investigated by means of multivariate analysis of morphological characters. We summarize the literature concerning this species, with particular emphasis on separating information concerning N. siamensis from that relating to other Asiatic cobra species. This species is of considerable medical importance, and we present case histories of local envenoming and snake venom ophthalmia.