Do you have any side pics of the puffer, and was the fish kept in pure fresh or brackish? What would you assume the total length of the fish was? I'm not a puffer expert, but my best guess would be a Ceylon puffer, although I have my doubts.
I don’t have more pictures, as I left the shop now. It was kept in freshwater. But not sure if this one is a brackish water fish or freshwater. The owner didn’t know it himself