In my experience:
PUL is not breathable, therefore it's hotter. However, you're not likely to have leaks.
Fleece is polyester but still breathable, therefore it's less hot than PUL. However, it is a much thicker material so it will be warm. It is subject to compression wicking (not good if your child will be sitting much).
Wool is breathable and a natural fabric, so it's much cooler all the way around. Also subject to compression leaking.
I live in a pretty hot & humid area, too ... not as bad as Bangkok, but the SE Georgia swamps have their moments.
In the summer around the house, dd goes topless & coverless ... just a snappied or pinned pf. IMO this is the coolest option of all, aside from naked (which we also do a little of every day!!). Next best, and what we do for trips into town, etc., is a cotton top, pf, and wool soaker. My mom made dd a few thin fleece wraps that she prefers to use, but I like the wool better. I also have some PUL wraps, but I just got them a few weeks ago. We haven't used them in really hot weather yet, so I'm not sure how we'll like them for that.
I hope that helps some.
PUL is not breathable, therefore it's hotter. However, you're not likely to have leaks.
Fleece is polyester but still breathable, therefore it's less hot than PUL. However, it is a much thicker material so it will be warm. It is subject to compression wicking (not good if your child will be sitting much).
Wool is breathable and a natural fabric, so it's much cooler all the way around. Also subject to compression leaking.
I live in a pretty hot & humid area, too ... not as bad as Bangkok, but the SE Georgia swamps have their moments.

I hope that helps some.
