[jsb5717]

I don't know for sure but the drain, which would have a compression seal underneath the ring to seal it to the shower floor, might be threaded into the pipe below the shower but since it's ABS the pipe is likely glued in. You would most likely have to cut the drain pipe in order to unscrew it from the drain.

While it likely isn't too difficult to do that I might be tempted to first try a little Flex Seal caulk underneath the shower where the flange seals against the shower floor. If it's a small leak that might take care of it.