Itinerary help Krabi/Samui/Chiang Mai

Hiya currently planning 3 weeks. Want to see lots but cautious not to travel every 3 days! 28M

Not planning to ride a moped unless I can find a local lesson to feel comfortable.

Arrive BKK and go straight to Ao Nang arriving late eve.

• 5 Nights Ao Nang (4 full days) - including island hopping 2 days Railay Beach day trip, other activities around Ao Nang. (Is 5 nights too many? Decided against 2 nights in Phi Phi and will just do it as a day trip )
• Planned to go to Ko Lanta but now thinking to so Samui for more to do… Can support up to 6/7 nights in Samui - but should I split time into Ko Tao and Ko Pha Ngan? All 3 might be a bit much to explore and I may not be on moped? Could split 4 and 3 nights each. Will be there during full moon time, not huge on party/drinking but kind of tempted to check it out and the atmosphere but could be swayed if time on the other islands are better.
• 5 nights Chiang Mai! Have heard so many good things.
• 3 nights Bangkok to end. Have been

Let me know your thoughts and if to add/reduce tome anywhere :)