It's virtually impossible to travel in Asia and not come across these guys:
Macaca fascicularis, commonly known as long-tailed macaque or crab-eating macaque, is the most common primate in southeast Asia; there are at least 10 recognized subspecies, although the differences between them are subtle. Despite their name, crabs are not their diet's main dish (nor eyeglasses!), being oportunistic omnivorous and feeding in a variety of animal and plant sources.
They live in social groups, with more females than males, and there's a clear dominance hierarchy among the females and the males of each group. Females tend to stay in the group they were born in, thus forming the core of the group. Males leave the group when they reach sexual maturity.
As most primates, they are highly intelligent. In some touristic attractions, where sometimes large numbers of monkeys are present, the interaction with humans can lead to you being relieved of some of your not-so-secure items so... heads up! They can be funny to watch and interact with, but they can be lightning fast! :)
Photos taken with Canon SX50 HS