Vandoo beat me to it.
To answer the question,
soft-shelled turtles are essentially freshwater, and they are increasingly rare, especially the large ones like we see here. There are species all over the place (Asia, Africa, North and South America), so I can't give you a locality from the shell. Hopefully someone else will chime in with location information. My guess is Indian subcontinent (India, Pakistan, or Bangladesh).
Best,
F