I only spent 2 days in Thailand, so I can't help you much. I know it is still monsoon in August (more details here
), but as others and I have experienced, monsoon is usually not that bad. It rains everyday for a couple of hours and then stops. But some days can be worse than others, unpredictably though.
Livefreeordie knows Thailand pretty well. If he doesn't respond to your thread, try sending him a personal message.