bunners75 - Check both LAX-NRT and SFO-NRT for upgrade availability (R space). You will not be able to upgrade the NRT-BKK leg, as that is flown by NH (since UA cancelled their NRT-BKK flight). Your flight is March. I would advise against buying a ticket now, unless you see confirmed upgrade space available.
If you buy a W fare and do not get upgraded, then of course there will be no refund.
BTW - Welcome to FlyerTalk.