Pangasius sutchi is just an old synonym, no longer in use. Pangasianodon hypophthalmus is the new name. http://www.planetcatfish.com/common/species.php?species_id=172
They are the same fish AFAIU. After revision, the IDSs are the only close relative to the gigas.
They are the same fish AFAIU. After revision, the IDSs are the only close relative to the gigas.