Where to go, few days in Sept

You should try Thung Yai Narasuan, you would love it. Great camp ground, right next to the car. Real wilderness feel too. Its about 6-7 hours in total from Bangkok.

I don't know how it looks like inside the park, but I can give you some good news which most likely concerns most of the park. It has been very long rain sessions here in Kaeng Krachan Town for last 5-6 days. It rains in average 7-10 hours a day, sometimes it continues until early morning hours. Like today, it started rain very intensively before 4pm, it still continues with average/light rain 8:30pm. It is constantly cloudy, very humid, mist covering mountain tops most time. :)

Humm.. Perhaps time to pack and move further south.. :(