I myself hate these noon/early afternoon flights from Europe to BKK / Asia because it is too early for sleeping and when you land in BKK in the early morning you feel very tired (like a zombie!) and most likely you can't check into your hotel before in the afternoon. I promise you, it will feel like a looong first day in BKK; absolutely dreadful IMO. I prefer to depart on one of the evening flights from Europe and arriving in the afternoon the following day in BKK. You are able to sleep much better onboard and there is still plenty of time left on the first day for dinner and going out (no time for sightseeing though). I feel it much easier to adapt to the new time zone when do it this way.