Background: Natural products are becoming important alternative medicines for diabetes treatment. Many Bauhinia plants in Thailand have been used in Thai traditional medicines for diabetic patients. Bauhinia plants have been reported on anti-alpha-glucosidase activity. However, Bauhinia pottsii var. pottsii G. Don which is a local plant in Southern Thailand has not been reported on antidiabetic activity and phytochemistry. Hence, it was selected for further study. Objectives: Isolation of chemical constituents from B. pottsii var. pottsii and determination of their biological activity on alpha-glucosidase inhibition. Materials and Methods: Chromatographic techniques, enzymatic assay, and molecular docking were done in this study. Results: A new stilbene derivative, 1,3-benzenediol-5-(-2-phenylethyl)-6-(2',3'-butanediol)-3', methyl (1) and five known compounds such as 3,4-dihydroxybenzoic acid (2), quercetin (3), 3-O-methylquercetin (4), a mixture of beta-sitosterol and stigmasterol (5), and 3,4,5-trimethoxyphenyl-beta-D-glucopyranoside (6) were isolated from B. pottsii var. pottsii. The plant extracts and isolated compounds were determined for anti-alpha-glucosidase activity. The results showed that the compounds 2, 3, and 4 were inhibited alpha-glucosidase enzyme activity with inhibition concentration at 50% (IC50) values of 3.637 mM, 0.486 mM, and 0.292 mM, respectively. While positive control, acarbose exhibited IC50value as 0.166 mM. The mechanism of action was proved using computer molecular docking. Compound 2 was predicted as mixed-type inhibitor, whereas compounds 3 and 4 were predicted as competitive inhibitors. Conclusion: This study will be the first report of phytochemical and biological study from B. pottsii var. pottsii including the first report of new compound.