Kaeng Krachan in august

I am not a birder but I would think if you just have a few days then birds would be your target. 

The natural choice would be the birding hides that are outside the park and you can arrange with one of the various birding guides, or turn up on spec (Baan Song Nok accepts one just turning up but I think some of the others have booking deals with the local guides). I would anticipate that with the closure of Panoenthung for the last year, the local guiding operations have really been exploring whats available outside the park and would have a very very good knowledge.

I have never really been a fan of Pala U as its essentially a waterfall day tourist site but with a good chance of elephants esp approaching dusk. As you are going to Kui Buri though you have the elephants covered in a much nicer natural setting as well as a higher chance of seeing them as well as gaur.

"The Dam Viewpoint" close to headquarters is just a view, no wildlife, its in the town/tourist area.

I like Laem Pak Bia and the also the Kings Project which is next to it. There are quite a few good write-ups on the various birding sites for this already (Northernthaibirding, Thaibirdspot and Thaibirding all have good write-ups) already. The bats are usually only visiable on the Laem Pak Bia site (next to sea) but theres a host of birds also in the "King's Project" site and its settlement ponds and mangroves.

Cha-am forest park - had no idea this existed so cannot comment. Same Nayang bat cave. But this is probably because of the type of photography I do, I tend to stick in the deeper recesses of the park.

Hopefully some others will share their recommendations as I know the park interior well but not the surrounding areas.