I would do the First class... you get F for BKK-HKG-<USA gateway>... <USA-Europe>... LHR/CDG/FRA- HKG-SYD/MEL... MEL/.SYD-HKG-NRT-HKG-BKK

That's at least 9 out of your 20 segments; over 70 hours in-seat time. More if you do DXB or CAI in Europe.

No doubt in my mind that the extra would be worth it.

Having said that, Thailand is not such good value for AONE as it is for DONE, it is quite a big step up. But even then it is only an extra US$30 per hour for F, and I reckon I could almost cover that in Krug, Tignanello, caviar, and kaiseki, never mind the extra space and comfort.