If you want to see orang utans the Sepilok sanctuary in Sabah is the one to go to. It’s the best of its kind in the world for orang utans. You can do other jungle activities there as well.

(In fact, the jungle experience can be so authentic ‘cos the virgin jungle there is so dense, even a British special forces team got lost in it once and had to be rescued after a week or something. Heh heh.)

For a more “user-friendly” jungle experience, I’d say a trip to the Taman Negara (National Park) in Pahang on the Peninsula should give you plenty of jungles and mosquitoes. :) They have orang utans there, too, but the peninsula is not a natural habitat for them. So the ones that are there were probably from Sabah originally.

For a scarier jungle experience, the Belum forest in Perak would be it. That is prime virgin rainforest, older than the Amazon, and virtually unexplored. That’s the forest where there are man-eating fish living in the primordial lakes. But I don’t think it’s open to casual visitors, though… especially foreigners. Something to do with poachig by bio-tech companies.

Ask another Q if you like. But I’ll be away to Penang for the weekend so might take me some time to respond.

I recommend that you go to Sepilok and definitely stay overnight. That way you can see the orang utans twice.

The first time it will be very crowded with other tourists. The second time—much less so. You can rent a nice, clean (but basic) room there and also eat there. So you arrive, eat, sleep, see the orang utans twice, maybe even stay another night (not necessary) ... then spend a day in Sandakan.

Fly over to Mulu, maybe? I think you have to fly by way of Kota Kinabalu from Sandakan. Book your internal tickets there in Malaysia.

Ruhayatx is correct—you can see the jungle in Taman Negara w/o leaving Western Malaysia. But … it might take you as much time to get in and around T.N. as it would to fly over to Sandakan!

Check the schedules and decide for yourself.