When performing OBB-OBB intersection using SAT, the suggested approach for generating multiple contacts is to find the coincident features and perform clipping - either edge against edge, or face against face, using the sutherland-hodgman clipper, after the SAT returns the intersecting features. This will return one (edge-edge) or more (face/face) contacts.
Dirk Gregorious of Valve covers this really well in his GDC2013 presentation. You can find one here: http://twvideo01.ubm-us.net/o1/vault/gdc2013/slides/822403Gregorius_Dirk_TheSeparatingAxisTest.pdf
I would recommend reading his paper, but essentially he suggests the following steps for face-face (his words not mine)
- Identify the axis of minimum penetration using the SAT (this defines the reference face)
- Find the most anti-parallel face on the other shape (this defines the incident face)
- Clip incident face against the side planes of reference face
- Keep all vertices below reference face
For edge-v-edge he suggests:
"If the axis of minimum penetration is realized by an edge pair compute the closest points between the two edge segments and are done."