Today I went to Cool Play Forest specifically, and here are a few tips for others.
1. It's quite remote, and the mountain roads aren't easy to navigate by car. However, no taxis would come when we left, and the taxi drivers waiting there were asking exorbitant prices, which was completely unacceptable.
2. The last picture shows my shoes, which are practically ruined, as are my clothes and pants. It's best to bring a second pair of shoes and clean clothes and pants.
3. Shoes can get wet, so it's best to wear moisture-resistant, hard-soled mountain boots. I saw the guides wearing those. I wore soft-soled wading shoes, which weren't particularly good and were uncomfortable when wet. My child wore Keen wading shoes, a better brand, and seemed to have a better experience, as they have hard soles.
3. I have to mention clothing. Although the temperature inside the cave is around 16 degrees Celsius year-round, which sounds quite cold, there's really no need to bring overly thick clothing. I don't even need a jacket; a thin sun-protective jacket is just the right thickness. I was constantly moving around, so I didn't feel cold at all. I was so disappointed with my large bag today; a short-sleeved shirt would have been just fine.
4. It's best to travel light and bring a small waist bag, not just a backpack. There were a few places that were too low, and my backpack got really dirty from scratches.
5. The official insect repellent didn't seem to be very effective; there didn't seem to be any living creatures in the cave.