Note: Sanctuaries are different to National Parks in Thailand, Thailand currently has established 39 sanctuaries and access is more restrictive as their role is as a sanctuary for wildlife rather than a park for the nation. Some sanctuaries do allow limited access to tourists.
"Access to the Thungyai reserve is harder, as the roads are poor. Take the route Thong Pha Phum-Sangkhla Buri near Huai Suea to Khli Ti Village, a distance of 42 km. After that, there is an intersection leading to the Wildlife Sanctuary Headquarters at Huai Song Thai another 40 km.
There are 3 permitted points for staying overnight. The first point is in the area of the sanctuary office, including 3 houses with a capacity of 10-30 persons and the training building with a capacity of 80 persons. The second point is at the Cyber Ranger Station, and the third one is at the Huai Mae Di Ranger Station.
There is no mention of camping. I am assuming that the three houses are located at Thungyai. Can you overnight at the Cyber (waterfall) and Huai Mae Di (with permission?). Lastly are the last two in Thungyai or Huai Kha Khaeng?
"Can you overnight at the Cyber (waterfall) and Huai Mae Di (with permission?). Lastly are the last two in Thungyai or Huai Kha Khaeng?
They are in Hua Kha Khaeng. Hua Mae Dee you can camp no permission needed. Cyber has facilities but never seen anyone camping there - the access area is so small (about 300 meters trail the waterfall) not sure if it would be worth while. Being a waterfall its busy at weekends, esp with the local kids.
As Paul mentioned, the 3 locations mentioned are in Huai Kha Khaeng, not in Thung Yai. For wildlife watching you want to be at the head quarter area in Lan Sak, Cyber waterfall will not be of interest. And I think you won't see much in Mae Dee either.
Camping is no longer allowed at the HQ area in HKK since last year (2016) after a camper got injured due to an elephant attack on the camp ground.
Best to stay in a nearby resort and just do day trips in and out each day. Make sure to rent a car, because without transport it will be a major disappointment.
I have never been to Thung Yai. It is high on my wish list. If I am correctly informed Thung Yai has a camping area which is open to visitors without special permission (but don't trust me on my word, I haven't tried it myself).
I do not know the exact location of this, and I do not know what wildlife watching opportunities there are around there. I know some people have had great sightings there, but of course those results do not necessarily mean anything.
One more thing. I do not know how many places you have visited already in Thailand, but if this is one of your first visits I would like to recommend not to exclude visiting some of the more popular national parks. I know many people want to visit remote parks with few tourists but the best places to actually see something, not to mention to actually be able to do more activities, are in the the national parks like Khao Yai and to a certain extend Kaeng Krachan.
I made the same 'mistake' on my first Thailand visit. I skipped Khao Yai and Kaeng Krachan because these were supposedly some of the more popular parks. Luckily I got ' stuck' in Thailand ;-) and got another chance to learn that these parks are popular for a good reason.
We are local and I am looking. Not so much for stuff to see. More so, that which is not seen. We have done a quick trip to Huai Kha Khaeng and have taken the back road to Khao Laem. I saw the turn off to Thungyai and would be most interested to know if anyone has tried it.