You are not pestering me at all, by the way, thank you for pointing me to your other post! Very interesting!
As to age group, I'm not sure as this will be my first holiday with Just You and on my own to that matter! My username gives you a clue as to my age (birthyear!) By reading the other posts on this forum, it would seem that all ages are welcome and indeed present.
As to internal travel within Thailand, I am returning to Bangkok airport with the rest of the group and flying on from there. I am still in the planning stage at the moment but will probably fly with Thai Airlines as I know & trust them. I plan to return to Bangkok at least 1 day before my flight home so that I know that I will be available to catch the Flight & not be stranded! I figured that one day will allow me to catch a train or bus should I miss the internal flight for any reason.
The Thai Airlines website is very easy to use!
Hope this helps
Andy