We describe a new cave-dwelling species, Cyrtodactylus sanook sp. nov., from Tham Sanook, Chumphon Province, southern Thailand, characterized by a maximum SVL of 79.5 mm; 18-20 longitudinal rows of dorsal tubercles at midbody; a continuous series of enlarged femoral and precloacal scales, no femoral pores, three or four precloacal pores in males (no pores in females), no precloacal groove nor depression; 19-20 subdigital lamellae on 4th toe; transversally enlarged subcaudal plates; and 6-7 irregular pale narrow dorsal bands between limb insertions. It seems endemic to this cave and is the 7th Thai Cyrtodactylus species that is known only from a cave environment.