We'll be flying from BKK home to USA, but we have 12 hours in Haneda (6a-6p).
Will we have time to get out and see some sights? Or should be plan on being stuck in the airport?
You’ll have time for a visit to Tokyo. www.japan-guide.com has the details of what to see/do in Tokyo.
What will you have done in initial 3 plus days? Lots of usual suspect sites within easy reach of Haneda.