I recently bought a Thai basil plant. After I bought it, I noticed that one of the leaves had what looked like holes, although the middle of the hole still had transparent dry leaf left. I didn't think much of it until I noticed another leaf with the same problem and it was curled. I removed the leaves, but today several more have developed this issue. They haven't curled yet, but they are developing the transparent "holes." Also, there is black stuff that resembles fine soil or bug feces under the leaf. Any idea what this might be? I live in Taiwan, a warm humid climate.

Definitely caterpillar scat. Leaf skeletonizers do that to a leaf, if you see little moths anywhere they are the culprits and are laying more eggs under the leaves of the basil. Check your plant and the soil around it as they will drop into the topsoil to hide. It takes spinosad to get rid of my cutworms, armyworms and skeletonizers.