They are monkeys. To be precisely complicated, they become long-tailed macaques, crab-eating macaques, 长尾猕猴, 食蟹猕猴，etc.
They are as invasive as humans, or vice versa, but they can always disguise themselves as The Thinker at the same time,
or show their disdain for the uninterested DSLR.
They are very common in Malaysia, I meet them every time I visit Cerok Tokun, and this time at Batu Caves.
"Batu Caves is one of the most popular Hindu shrines outside India, dedicated to Lord Murugan. It is the focal point of Hindu festival of Thaipusam in Malaysia." (Wikipedia).
We made a detour to visit this place during the last trip to Bukit Tinggi.