SAT Tower Controller reported a runway incursion.

Report 1 | Narrative: I had an aircraft one mile final for Runway 13L and as I was scanning the surface area I noticed Aircraft X crossing Runway 13L at taxiway N. I instructed ground of the deviation and GC (Ground Control) immediately prompted Aircraft X to clear the runway.There is a big communication barrier with foreign pilots and the placement of our customs ramp and FBOs requiring numerous runway crossings. Some sort of ground radar may not prevent the incursions from happening but it may be the difference in catching one of these where we might otherwise not.

Report 1 | Synopsis: SAT Tower Controller reported a runway incursion.