Thank you all for your replies.
If Chiang Mai is a no-go then, what alternatives would you recommend to enjoy Thailand beyond the south and the islands, where we’re definitely planing to spend a large chunk of our time over our 17 night holiday.
After Bangkok I’m considering Ayutthaya, and perhaps Kanchanaburi. Are the national parks in that area worth exploring?
And what about the area east of Bangkok, like Khao Yai?
With 17 nights, I was thinking 3 nights in Bangkok, and then 2-3 nights experiencing an alternative side to beaches and seaside.