Xylariales members have conspicuous to inconspicuous perithecia with unitunicate asci. The most known species are endophytes and saprobes, known to produce secondary metabolites with fundamental importance in the pharmaceutical and chemical industries. The current study collected samples from decaying barks of Quercus kingiana at Doi Inthanon National Park, Thailand. Based on morphological features coupled with combined gene analyses of ITS, LSU, rpb2 and tub2 sequence data, the isolates were identified as Xylaria karsticola and Jackrogersella minutella, belonging to Xylariaceae and Hypoxylaceae, respectively. This study provides the first geographical records of X. karsticola and J. minutella in Thailand and the first records of these species on Quercus kingiana.