search google and this website:

Sepilok Orangutan Rehabilitation Centre
Sabah
Malaysia

personal experience

I have visited this place many times with tour groups.

orangutans

The main reason most people come here is to easily see Orangutans in a relatively natural rainforest setting. Food is put out at a platform every day at the same time, and the animals are free to come and go as they please.

the Borneo Orangutan (Damon Ramsey)

Because there is very well developed and undisturbed rainforest around the orang-utan centre, there is also good bird and other mammal watching.

a Sunda Giant Squirrel scurries along the wires above the Orangutan feeding platform (Damon Ramsey)

Recently, a new enclosure has been built to house sun bears, a small bear native to south-east Asia.

Sun Bear (Damon Ramsey)

Updates
Throughout the virus I am working in Australia on and off as local borders close, mostly in the Kimberley with Coral Expeditions (May-September). If you can't go travelling until everything settles down, then until then, here I am doing online guided walks for Noble Caledonia and online lectures for Silversea.