For managing jetlag the key is timing in the arrival zone. So 841 departs at 9pm Bangkok time, 831 departs at 2am Bangkok time.

What I would do is stay awake all night in NYC the night before and then get 841. Get on the plane, take a glass of Krug, and sleep until about 7am BKK time. Then you have 6 more hours on the plane and two meals: breakfast and lunch.

Remember this is First - you can eat whatever you want whenever you want, so just tell the crew what you would like to do before you go to sleep and they will have it all ready for you. I can't find an F menu for 841, but the J menu here shows that they load breakfast type things in J, so presumably they do in F too.

So have breakfast at breakfast time and lunch (Krug, caviar, etc) at lunch BKK time.