I take this leg all the time.
UA/LAX to NRT. Then ANA to BKK.
Coach for 7 more hours sucks after you have already been sitting.
It is pretty typical coach. They do have a decent entertainment system.
The food is pretty poor.
My last flight this year I changed the route. LAX to SFO then to Hong Kong.
Form HK it is only 3 hours to BKK. I use Thai air(star alli member) with miles or just pay.
It is about $300 RT HK to BKK.
I am booking this route thru HK for just about all my trips in 2015.