I'm attaching here a photo of a paratype of S. hefferni and a sketch of the pronotum (courtesy of Joan B.).
I can't absolutely say that your specimen is S. hefferni, because I have made more than my share of mistakes when working with the green Callichromatini from Borneo. But... I also can not find another species in my collection that it is more resembling.
Unless you have been able to study a series of specimens, it is hard to identify this genus. I have 6 of the 8 species known from Sabah, but only 1 or 2 of each species.