I think para 22 is quite clear. The fare is constructed over LAX - it doesn't mean you FLY via LAX, but they're saying they're using the BKK-LAX F fare with thwe add-on value of LAX-JFK to give you the fare basis you pay even though you're flying via NRT (since NH don't fly LAX-JFK anyway).
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RichardMEL, UA 1P (It's Time to Fly)
A Star Alliance Member.