Vietnam/Laos/Thailand tips

I am considering doing some volunteering in one of or a combination of Vietnam, Laos, and/or Thailand, particularly in August or early September. How is the weather during this time of year, what are the bugs like, what are things to expect/look out for, etc? Any general tips, pointers, or things to consider would be incredibly helpful. I have started doing some research online, but if anyone has any personal accounts to share, I would love to hear them!