A buddy of mine had the same low opinion of Krabi. Ao Nang (in Krabi) is a really nice place. What's more Krabi is the gateway to several other places.
visa run. Pop over to neighboring country. I am not sure what the rules are today. Last I knew you had to fly but the rules are changing and will likely be different when it matters most to you.
immigration will hunt you down. If you check into another hotel use fake IDs.. Do not leave your room without proper disguise.
I have been here 8 years and never once has immigration come found me, I suspect they've never looked for me. It happens sometimes but its rare.
If you do change rooms, hotels, towns, and you plan to get a visa extension, you will want to make sure wherever you go, they do your TM30 (inform immigration where you are staying)..
It appears to be about 20 minutes for your hospital. I found it to be comfortable and reasonably priced. Its not walking distance to anything but it's a short taxi ride to everywhere.
All the other hotels I use in BKK are cheap and not particularly comfortable, if you need those kinds of recommendations?
When I did ThaiPass in January it had taken 3 weeks. Things have changed and supposedly its more streamlined now but I would not wait until last minute.