AO absolutely not, it responds to proximal polys only, GI wouldn’t be the same it will give a much more varied (realistic) light distribution.
You could do it with SubSurface Scattering in the Luminance channel but it will make the frontside (the side facing the light) brighter too. Possibly a combo of SSS and Backlight, the only other channel shader to respond to light position – (that I can think of at the moment).
Otherwise it’s the basics, put a light in the scene that illuminates the other side a bit. No shadow so it’s evenly distributed and probably limited with the Scene tab so it doesn’t light everything.
Unless there’s a 3rd party shader out there that I’m not thinking of or am not aware of