In this study, an antimicrobial-producing Actinomycetes PJ90 was isolated from forest soil in Suranaree University of Technology, Nakhon Ratchasima, Thailand. The morphological characteristics and 16S rRNA gene analysis revealed that isolate PJ90 could be classified as Streptomyces triostinicus. The isolate PJ90 exhibited antimicrobial activity against Staphylococcus aureus TISTR1466, Staphylococcus epidermidis TISTR518, Bacillus subtilis TISTR008, Candida albicans TISTR5779, Candida tropicalis TISTR5174 and Saccharomyces cerevisiae TISTR5049. To our best knowledge, this study constitutes the first anti-bacterial and anti-yeast activities of Streptomyces triostinicus isolated from soil in Thailand.