Which jungle in SE Asia? Thailand, Borneo, Sumatra?

I have a trip to Bangkok Thailand soon and have been racking my brain on where and how to take a nature-related personal trip while I'm in SE Asia on company dime. After some online and soul searching (is it the beach, whale watching, etc.), I've decided I want to see animals in a jungle. (I was fortunate to have experienced a safari for the first time in Kenya last year that changed my life!)

Which jungles/forests are the best in SE Asia for jungle/forest treks and guided tours to see wild animals? I'd rather see them in the wild than visit nature reserves or sanctuaries.

I've been doing some online research and am looking at the following:

Borneo (Tanjung Puting National? Danum Valley? Deramakot? Kinabatangan River?)
Thailand (since I'll be in Bangkok; Khao Yai, Kaeng Krachan, Khao Sok*)
Sumatra (Kerinci, Gunung Leuser)

Notes:

*I know orangutans are all the craze in this part of the world, so yes I'd love to see them of course, along with those elusive cats, leopards, etc. I would also be really excited to see birds (hornbills!), elephants, rhinos (Sumatra?) reptiles, insects, and other mammals, etc. too though. I don't want this to be an orangutan-only trip.
**Khao Sok feels more like something for scenery and the scene on the water.

I'd prefer you simply share forests that you think are best for wildlife viewing in SE Asia, and I can see if I can fit it into my logistics. If you're curious, it will likely have to be a short trip -- probably no more than 4 nights -- unless I can find a way to stretch it out and see more animals.

If you have a top 3 list, especially from what I've shared, I'd really appreciate it! Of course, if there is something else outstanding that I'm missing, please fill in the gap for me.

Thank you so much!

Author: yk4787