Definitely a skink. However I am not very familiar with the various species. My guess would be the Striped Legless Skink, Isopachys anguinoides. But I will ask a friend of mine to see if he can confirm this.
I have also discussed this with a good friend of mine, and he came up with the same ID, Striped Legless Skink, Isopachys anguinoides.
Cool find, I have yet to see one. I know they should be around Kaeng Krachan as well, but have still eluded me.