The Neogene period witnessed the radiation of modern crocodylian genera, as evidenced from their fossil record in intertropical zones. Despite its recognition as a modern biodiversity hotspot, South East Asia remains undersampled for that age bin. Here, we describe a new crocodylian from northern Thailand, Antecrocodylus chiangmuanensis n. gen. n. sp. from the Middle Miocene lignite seams of Chiang Muan and refer to it other specimens from the nearby lignite seams of Mae Moh. The holotype specimen preserves the posterior half of the skull and mandible. Anatomical observations are aided by medical computed tomography. A phylogenetic analysis places the new taxon in a basal position relative to Crocodylidae. This discovery highlights the underrated fossil record of Neogene crocodyloids in Asia compared to Africa or Australia and allows us to reconsider palaeobiogeographic relationships between supposed endemic clades.