Ugh, I love a good drama with a badass villain too (preferably as the main character) but they're so hard to come by, or almost non-existent.
I second Behind Your Smile, Empress Ki and Secret. Definitely make sure you put these on your list—they fit your criteria almost perfectly.
The only Thai lakorns I would recommend from the ones already mentioned would be Kleun Cheewit and Sanaeha Sunya Kaen. Especially the latter. Just like in Secret, the male lead in SSK is seeking revenge for the death of his fiancé, ends up tormenting the wrong person and in the process falls in love with her.
You can also check out Game Payabaht and Leh Ratree. Don't even go near Jam Loey Rak or Sawan Biang, especially not if you're new to lakorns. You'll just end up getting offended and annoyed. Generally, don't expect intelligent and well-woven stories from lakorns, watch them for the sizzling romance and the chemistry between the leads—Thai lakorns are unparalleled when it comes to this.
Sealed with a Kiss (Chinese) is another revenge themed drama you can consider. Although, probably not for the faint of heart (and definitely not for the one who is looking for a sweet, cutesy romance to watch).
Easy Fortune Happy Life—I have a feeling you might like this one.
Hope this was of some help. Happy watching!