The lowland area of southern Vietnam contains a high diversity of corticolous, crustose lichens, particularly in the family Graphidaceae. Two species, Acanthothecis verrucosa S. Joshi, Upreti & Hur and Graphis exuta S. Joshi, Upreti & Hur, are described new to science. Acanthothecis verrucosa is characterized by a verrucose, olive green thallus containing irregular to shortly lirellate apothecia, hyaline to brownish proper exciple apically lined by robust periphysoids, muriform ascospores, 30–70 × 15–20 μm, and the presence of psoromic and subpsoromic acids. Graphis exuta is characterized by a smooth, greenish white thallus, simple lirellae lacking thalline margin, entire labia coarsely white pruinose towards slit, muriform ascospores, 20–35×10–13 μm, and norstictic acid in the thallus. A new name, Acanthothecis yokdonensis S. Joshi & Hur, is proposed here for the species Acanthothecis salazinica S. Joshi & Hur, a later homonym of A. salazinica van den Boom & Sipman. In addition, 34 species from Vietnam are newly reported. A world key to the group of Graphis species characterized by short, simple and sessile lirellae lacking or with basal thalline margins (nuda-morph) is presented.