It's a hot humid place with a 100% chance that it is going to rain so you are going to get wet. You'll be riding at relatively low speed in a crowed and very financially poor but spiritually rich environment. Take a guess …
Seriously leave the expensive "summer" gear at home, bring mesh or motocross gear that breaths well, cheap easy to pack and will protect you enough in a get off. Joe Rocket mesh jacket & pants with MX boots will serve you well. I've ridden in Laos, Thailand & Cambodia and this is what worked for me.