Coenogonium coronatum, a lichen-forming ascomycete, is presented and described as new to science. The species differs distinctly from other taxa by the formation of a crustose, smooth thallus and the densely pilose apothecia margins. Photographs of thallus morphology and apothecial anatomy illustrate the new species from the palaeotropics. A key to the Coenogonium species known from Thailand is also included.