I have a flight tomorrow that might leave from either A or G (won't know until tomorrow). I would prefer to use the UA or SQ lounge (int'l flight) before departure, and I can use Precheck which I believe is only available at T3 which exits near the bridge to International G (not A).

If I go through security and walk to Int G and use the SQ club, do I need to exit back to the main terminal and re-clear non-Pre security on the A concourse side, or is there a sterile-side path or shuttle between the two concourses?