Just another opinion from someone who is in and out of Tokyo all the time... Since you would be in F there is a high likelihood that you will get off the plane first and also possibly be escorted to the next flight by a representative from NH. Also -- you will have access to the excellent TG F lounge (suites) in BKK (if open - not sure about that). NRT is a VERY efficient airport and I would not hesitate to take these flights if that is your preference. The lounges in NRT are nothing to write home about -- even the NH F lounge is sort of average - so don't worry about missing that -- although I think that you will have plenty of time to get through security and enjoy the NH F lounge for a glass of champagne / noodle bar visit...