(Edit: My thanks to Ayuwat Jearwattanakanok for pointing out my very obvious error: originally this was named Ratchet-tailed Treepie, an altogether much rarer species, when in fact I meant Racket-tailed – thanks Tun. ) With four Himalayan Vultures recently in Phetchaburi province I was very hopeful of something interesting during the two nights of the school camp in a resort, the Thanattichaburi Lake Resort and Spa, to the east of Kaeng Krachan National Park. In the end no raptors but one unexpected lifer in Racket-tailed Treepie. The long, slim tail with its “distinctive broad, spatulate tip”, ( The Birds of the Bangkok Area, Round) is what enabled me to identify this bird. Otherwise easily mistaken for a Drongo, especially when viewed at a distance.
Some Richards Pipits, very erect stance, lots of Olive-backed Sunbirds, a couple of Common Tailorbirds and some Chestnut-headed Bee-eaters – and lots of interesting calls in the dark. A Coppersmith Barbet was noteworthy simply because it was the first seen in over a year. Once a bird I saw very regularly.
Unfortunately my foot is playing up a bit at the moment so limited mobility. Hence little birding.
Dodgy Birds 
This year seems to be especially good for vultures. So many were also reported from northern Thailand. By the way, I’m a little confused with the treepie that you saw. I believe the one with spatulate tip is called “Racket-tailed” and the one with spiny tail is called “Ratchet-tailed”.
i think we saw a Racket-tailed Treepie at the “Pelican spot” near Wat Takrao a few years ago. But a very brief views of a flying bird.