score:3
This asks for a personal opinion, really, which is not ideal, here. But, something can be said about your planned destinations anyway.
If you have two weeks, it's enough to get a good idea about Bangkok, Chiang Mai and Krabi. I'm personally not a big fan of the Thai beaches, but that's personal. Many people love it.
More importantly, Chiang Mai, Bangkok and Krabi are three very different aspects of Thailand, so just for that they would be worth visiting. Bangkok is a bustling metropolis, Chiang Mai has a gorgeous climate and is a laid back feel in a beautiful setting, while Krabi is a popular seaside destination with all that comes with it, but also with gorgeous beaches.
You can take a decent night train from Bangkok to Chiang Mai and fly from Chiang Mai to Krabi (or close by), optimizing your time.
Sure, you can send two weeks in any of these places, but 3/4/5 days in each will also give you a very good feel for them and will pack a very decent punch.
(Note, that there are plenty of other places in Thailand that are also worth visiting, though.)
Upvote:2
Personally since you have limited time, I would blow off Bangkok all together and add those days to your Chiang Mai and Krabi stops. While Bangkok is different than say Frankfurt, it is still another big city like every other big city.
Chiang Mai is also a fairly big city, but has a small town feel to it when you are in the historical center. And armed with a bike (be it pedal or motor) it is easy to slip out of town on small roads to explore the countryside. Chiang Mai itself has a lot of neighborhoods to explore, temples, museums and cafes to check out.
For your Krabi stay are you thinking about staying in Krabi town (away from the beach) or are you pondering being at the beach in a place like Ao Nang? If at the beach, you may find your time too long, as Ao Nong and such are touristy beach towns. You can get some boat trips to places like Koh Phi Phi, but you can also get away by bike to explore the back roads through the Karst hills.