Monkey kokah (Presbytis siamensis) is a species of primate in the Cercopithecidae family.

It isendemic to the Thai-Malay Peninsula, the Riau Archipelago andSumatra. Four subspecies,siamensis (nominate), cana,paenulata and rhionis, are recognized here, but the taxonomyis disputed and in need of a review, and it has included P. natunae as a subspecies, or alternatively both have been considered subspecies of P. femoralis.