A Gram-positive, endospore-forming, rod-shaped bacterium, strain PD-A10T, was isolated from salted crab (poo-khem) in Thailand and subjected to a taxonomic study. Phenotypic and chemotaxonomic characteristics, including phylogenetic analyses, showed that the novel strain was a member of the genus Bacillus. The novel strain grew in medium with 0–14 % (w/v) NaCl, at 4–55 °C and at pH 4.5–9. The predominant quinone was a menaquinone with seven isoprene units (MK-7). The major fatty acids were anteiso-C15 : 0 and anteiso-C17 : 0. Polar lipid analysis revealed the presence of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, lysylphosphatidylglycerol, glycolipid and unknown lipids. The DNA G+C content was 41.4 mol%. The 16S rRNA gene sequence similarities between strain PD-A10T and Bacillus amyloliquefaciens NBRC 15535T, Bacillus subtilis DSM 10T, Bacillus vallismortis DSM 11031T and Bacillus mojavensis IFO 15718T were 99.5, 99.4, 99.4 and 99.2 %, respectively. Strain PD-A10T showed a low degree similarity of rep-PCR fingerprints and low DNA–DNA relatedness with the above-mentioned species. On the basis of the data gathered in this study, strain PD-A10T should be classified as representing a novel species of the genus Bacillus, for which the name Bacillus siamensis sp. nov. is proposed. The type strain is PD-A10T (=BCC 22614T=KCTC 13613T).