Found this on what to bring

"¢ Please wear non-slip shoes
"¢ Don't forget your camera/film
"¢ Bring a small backpack or bag with a change of clothes in case you get wet!
"¢ Also, depending on the weather, a raincoat and/or sun protection. "¢ Bring insect repellent
"¢ The itineraries are example of the activities that usually take place on the tours. The order of activities varies depending on the weather, timing and many other factors.

Should be in the 90's as May is at the end of the hot season, and the beginning of the wet season. not sure about the pith hat

Great post oldoldgit

I would have just answered wear mozzie cream, long sleeves and long pants at night to protect against Malaria biting mozzies... plus don't forget use mozzie cream during the day for Dengue fever. Perhaps a cardie for the hills.

I forgot about all the other enjoyable stuff like camera to record happy memories.

Just one thing... since we had terrible rains one year in Koh Samui we never leave home without a plastic poncho bought from the $2 shop in Australia... when the Heavens opened in Koh Samui there wasn't one to be had. However, I'm glad to report we take them everywhere now and they remain unopened
Cheers Geri

Not done the Khao Sok but have done a few days in a lodge in Taman Negara Malaysia. We found after a few days in the jungle with a mix of rain and sun that our clothes were not worth bringing back so we ditched the cheap ones. Some people wore walking boots others had proper walking sandles. If your activities include staying into the wee hours in a viewing hide then you may want something to take away the chill of the night if you've got acclimatised to the heat. We also found a few rehydrating drinks quite a godsend as well, as I've never sweated so much in my life. (you can buy sachets of the stuff over there but knowing Thailand theres usually some shop selling stuff even in the remotest places).

A torch can be quite handy as well, as might a foldable brolly.

Who knows you might even see the elusive sun bear.