While Erosa does indeed belong to the family Synanceiidae (stonefishes), so do the stingfishes (Choridactylus and Inimicus). In fact, looking at the fish, it actually closely resembles C. multibarbus with a LARGE mouth and no dactyls. Sizewise, it's close to the Red Sea Stonefish (Synanceia nana) at 5" - 6" max.
The fish in question is a Western Pacific species, and has been photographed in the Lembeh Strait. Sure seems like a lot of really cool fish hang out there!
As far as where Erosa lies in the toxicity scheme of things, I suspect that it's at least as bad as the stingfish, maybe more (I sure wish I could find that reference on scorp toxicity!). I'd treat the fish pretty much the same way in terms of handling.
Fish like this showing up suddenly is the exact reason "scorp hunters" need to have a QT ready to go at "cualquier rato"...