We described a new species of elapid snake genus Bungarus from the Tenasserim Mountain Range in Ratchaburi Province, western Thailand. Bungarus sagittatus sp. nov. can be distinguished from all congeners by having the combination of 15 dorsal scale rows; 215–217 ventral scales; 48–56 undivided subcaudal; prefrontal suture 2.4–2.6 times length of internasal suture; anterior chin shields larger than posterior chin shields; head of adult uniform black while juvenile black with small dim white patches on temporal and parietal areas; dorsal body black, with 25–31 white narrow bands, white and black bands at midbody covering 1.5–3.0 and 4.5–6.0 vertebral scales, respectively; dorsal body black bands not intruding ventrals or intruding ventrals less than 0.5 times of width of outer dorsal scales; ventral surface of body immaculate white; ventral side of tail white with a row of dark brown triangular patches on middle pointing posteriorly; tail relatively long, tail length/total length 0.140–0.143. Genetically, the new species has uncorrected pairwise divergences of ≥ 8.29% of the mitochondrial cytochrome b from other Bungarus species. Currently, the new species is only known from the type locality.