The white-thighed surili (Presbytis siamensis) is a species of primate from the family of old world monkeys (Cercopithecidae).

[1] In addition, the white-thighed surili contain four subspecies: siamensis (nominate), cana, paenulata and rhionis, are recognized here.

[4] Additionally, their tails – typically covered in dark fur – can extend roughly 58–85 cm.

[3] Alternatively, research suggests three species are endemic to Malaysia: P. siamensis, P. femoralis and P. robinsoni (Robinson's Banded langur).

[2] Through mitochondria DNA analysis, these three species are split into two separate clades: P. femoralis on its own, P. robinsoni and P. siamensis in the other.

[1] Researchers say several Presbytis species are affected by logging activities, although not all of them are recognized on the IUCN red list.

This species is seen in the public's eye as a value of science, genetics, forest sustainability, aesthetic, tourism, and a symbol of heritage.

[5] More research on abundance, ecology and behavioural biology of the white-thighed surili is vital to creating better conservation management plans.

[1] Moreover, education the public on illegal trade of primates as pets may combat the demand for the industry.