I think you'll find it is a straight thread 20TPI and probably 3/8, maybe 1/2", don't remember. Should screw onto a male compression coupling. So compression on one end and pipe on the other fitting should get to the point where you can hook up to most anything.
But that end of the regulator is intended to screw onto the paint gun, not the hose.
I probably have a half dozen of those laying around, most came with a HF gun. A lot of them look like a regulator, but are really just a flow adjustment. Surprisingly, the HF ones are real regulators.