This study aimed to identify the causal agent of cassava leaf blight in Thailand and to evaluate the biocontrol potential of Bacillus spp. isolated from the digestive tract of small millipedes. Symptomatic cassava leaves were collected from Maha Sarakham Province, Thailand, and a total of 32 bacterial isolates were obtained and classified into seven morphotypes. Pathogenicity tests revealed that isolates Mnbr-2 and Mnbr-22 induced typical leaf blight symptoms, with Mnbr-2 producing the largest lesion diameter (28.30 ± 3.50 mm) and therefore selected for further study. Based on morphological, biochemical, and 16S rRNA gene analyses, isolate Mnbr-2 was identified as a member of the genus Pantoea and was closely related to Pantoea stewartii, showing 99.75% sequence similarity. These findings provide evidence that Pantoea-associated bacteria are involved in cassava leaf blight in Thailand. The antagonistic activity of 28 Bacillus isolates against P. stewartii Mnbr-2 was evaluated using the agar well diffusion method. Several isolates, including Bacillus velezensis, B. cereus, B. safensis, and B. subtilis, exhibited strong inhibitory activity, with inhibition zones ranging from 25.00 ± 1.50 to 30.00 ± 5.00 mm. Cell-free culture filtrates of selected isolates also suppressed pathogen growth, showing inhibition comparable to that of streptomycin (100 ppm). Detached leaf assays demonstrated that B. cereus N5_TCR and B. velezensis N8_TCR achieved the highest disease suppression under both preventive and curative treatments, with inhibition efficiencies ranging from 91.35%-94.41%. These findings indicate that the selected Bacillus isolates possess strong antagonistic activity and may serve as promising candidates for the development of sustainable and environmentally friendly biocontrol strategies against cassava leaf blight caused by Pantoea.