Trail 6 is fairly bright, not closed canopy along a lot of it and of course the forest edge is very good in the mornings. I've managed to digiscope a lot of stuff there though sadly not the two pittas. On the whole, yes, you can achieve a fair amount. The Pittas, Forktails, etc favour the darker areas, you'll just have to enjoy them instead
I do see a lot of Thai photographers there and they do seem to have a great deal of success with some stunning results!