Okay, so I'm going back to Thailand for the 3rd time in a year - I've fell in love with the place.

So far I've seen Bangkok, Phuket and Phi Phi.

This time, I have just over 2 weeks to play with.

Not wanting to go back to Phi Phi, has anyone got any possible suggestions on where to go.
I'm more of a city person, but like a bit of beach (for a few days at most).

I was thinking of something like Bangkok (5 days), Chiang Mai (4 days), Koh Samui or similar (4 days) and then back to Bangkok for remainder.

Any ideas??

Sounds like you've got plenty of ideas already. What sorts of things do you like to do? I mean, what is it you love about Thailand?

Surely you've seen enough of Bangkok? If you must spend time there (and I don't blame you) save it for the end of your trip so you can do all your shopping then. Spend a few more days up north instead. After Chiang Mai, explore Chiang Rai. Head up to the Golden Triangle and you can do a quick trip to Laos and maybe Myanmar (if the border is open).

I really enjoyed my visit to Koh Samui, so I would have to recommend it, but I prefer the beaches of Phuket. If you're any sort of a party animal, consider Pattaya. I got dragged there a few years ago and found it to be not nearly as bad as I had imagined (and been told). The beach is generally wretched though.

I've recommended Ko Samet in the Best 2 night trip from BKK? thread. I won't reiterate what's already there other than to note that it's one of my favorite beach getaways in Thailand.