You can tell this was set up by AA - why not do LHR-SFO on BA instead of LHR-xLAX-SFO?

You could get a separate HKG-BKK-HKG ticket for a lot less that US$300+taxes (probably under $200 if you take Orient Thai or someone).

You would still have 4 free segments to use in Africa or NA - perhaps two round trips from SFO to somewhere.