A sooty blotch and flyspeck fungus with semi-transparent ascomata was discovered in northern Thailand. Its multi-loculate-like ascomata arrangement is similar to species of Lecideopsella (Schizothyriaceae), but ascomata lack a network-like arrangement. The new genus also has ascospores with appendages at both ends. Maximum parsimony, maximum likelihood, and Bayesian inference analyses of a combined ITS and partial LSU sequence dataset revealed that this new taxon is a member of the family Phaeothecoidiellaceae, but it is distinct from any other genera. Therefore, Translucidithyrium thailandicum gen. et sp. nov. is introduced here with descriptions and illustrations. The discovery of this new genus with sexual characters in Capnodiales will make contributions to the further understanding of sooty blotch and flyspeck fungal group.