Wow, I can't believe no one commented on this yet.
I didn't like Bangkok too much... Khao San Road is the pits, we have discussed that point many times on these forums.
I went to Nakorn Ratchasima when I was there last year:http://www.travelpod.com/travel-blog-entri...97380/tpod.html
If you like the jungle you will like it. It is not as busy and industrialized as Bangkok. It's probably on your way to Laos, you might like it.
Other than that, I have no ideas for you!
Read some blogs and see how other people did it, I'm sure you'll get way TOO MANY ideas.