I believe the animals have access to those trees with the platforms around the middle trunks but nothing beyond that fence line or behind the blue building. I think the containment is simply that there are no other trees close enough for the lorises to get to, I think the picture is a bit deceiving with how close the trees behind the blue building are.
I believe the point of this enclosure is mainly for the night 'safaris' that they do around the zoo where people can visit at night (though I didn't). During the day I don't think most people see the lorises because they stay inside the building, though there is nothing stopping people walking around on the grass to look at the lorises inside the building through the mesh, which I did. I have a picture of a loris in my next lot of pictures of Khao Kheow that I will be uploading shortly.
