Is sacroiliac pain treatable with cold laser therapy?

Probably not. Cold laser had very limited (several millimeters) permeability. Therefore it's unlikely any joint pain can be treated with this method.
I Suppose. Cold laser is still considered by most to be cam, however, cold laser may or may not be effective. I would not say that it would be specifically effective for the sacroiliac joint any more so than any other pain area, if it is indeed effective at all.