Correct, no security re-screening needed so long as you are flying UA from LAX to SFO and then connecting UA SFO to HKG. The airside domestic-to-international corridor is just beyond SFO T.3 Gate 75 and will go toward the right. Do not take the left exit just beyond the Centurion Lounge as that will take you outside of the secured area.

Once in the International terminal which UA uses for HKG, There is a GFL near gate 98, and a "regular" UA club near gate 94.
https://www.united.com/web/en-US/con...s/default.aspx