A Gram-positive filamentous bacterial strain that developed large campanulate sporangia at the ends of sporangiophores on substrate mycelium was isolated from bamboo forest soil in Thailand. According to the results of a polyphasic taxonomic study, our isolate had typical characteristics of members of the genus Actinoplanes. The 16S rRNA gene sequence analysis also indicated that strain A-T 6646T belonged to the genus Actinoplanes, being most closely related to Actinoplanes liguriensis DSM 43865T (97.61 %) and Actinoplanes octamycinicus NBRC 14524T (97.52 %). The DNA-DNA relatedness values, which differentiate the new strain from the most closely related species, were significantly below 70 %. The cell-wall peptidoglycan contained meso-diaminopimelic acid. The whole-cell sugars contained xylose and arabinose. The predominant menaquinone was MK-9(H4). The diagnostic phospholipids were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol. The predominant cellular fatty acids were iso-C16: 0, anteiso-C17: 0, iso-C15: 0 and anteiso-C15: 0. Following an evaluation of phenotypic, chemotaxonomic and genotypic studies, the isolate is proposed to represent a novel species to be named Actinoplanes siamensis sp. nov. The type strain is A-T 6646T (= BCC 46194T = NBRC 109076T).