Ascomycetes mushrooms are fungi that produce ascospores in asci and some with perithecia. Not only they have a role of decomposer in ecology but also produced some bioactive compound, anti-microbial activity, and cytotoxicity. This study aims to explore the diversity of ascomycetes mushroom species in para rubber plantations and to identify them by morphological and sequence analysis of the internal transcribed spacer (ITS) region. The results found ascomycetes mushroom consist of Trichoderma pezizoides (RP1, % identity 98.79, DQ835513.1), Daldinia eschscholtzii (RP2, % identity 100, MN310384.1), Cookeina sulcipes (RP3, % identity 98.44, KY094620.1), Cookeina garethjonesii (RP4, % identity 99.06, KY094622.1), Cookeina tricholoma (RP5, % identity 100, KY094619.1) and Xylaria terricola (RP6, % identity 88.42, MF577038.1). Most of the ascomycetes in this study have previously been described in Thailand except Xylaria terricola. Additionally, phylogenetic analysis of ascomycetes mushroom showed high genetic relatedness with reference strains. Therefore, the sequence similarity and phylogenetic analysis confirmed the identity of six ascomycetes mushroom species, and further study of bioactive compound from these mushrooms may be investigated for other applications.