I agree with Dave, I much rather prefer to be riding around Chiang Mai, only trouble is I do a lot of sailing both socially and racing in regattas so I prefer living down south for that reason, also enjoy the beaches. If you come into Phuket another option is forget about riding to Bangkok, instead go riding all around Southern Thailand, Krabi, Hat Yai, Songkhla, Koh Samui etc. Whilst these rides dont match up with the North, there are still some scenic areas, also at Ranong, you can take a long tail to Burma, where gin and rum is less than 1 Aussie Dollar a bottle. My Thai girlfriend was reading your original email and suggested she could help as translater if needed.
No worries whatever you decide, but I am available in november if you decide to make it to Phuket