East of Thais, in between the horse stables and Thais Troll Cave, there are 4 dead snakes by the rocks and fire fields. 3 of the bodies are stage 1, and 1 body is stage 2.
Edron Orc cave, -2 just east of the hole to head towards orc cults.
I am pretty sure there are other places to find snakes, and I am still working on finding a frog.
I will update this as I find more and more locations for each.