After 3 nights in BKK, then Phuket for 7 nights, all in Marriotts, we have 3 nights that are unscheduled at the momment and are looking for suggestions. We will need to be in BKK for that last night in order to leave paradise in the morning...Thanks for any suggestions. We would like a change from Marriotts, to more rustic/adventurous, may Phi Phi for two nights??? Please help. Thanks so much!

When are you going? Are you completely dedicated beach people? If not, Thailand has so much to see that is not beach that it would be a waste to skip parts. Also, have you made absolutely firm flight and hotel reservations? If not, you could go to Chiang Mai and fly directly to Phuket from CM.

What time of year? As weather could come into options. You could spend a few nights on say Koh yao island ( 1 hr from Phuket ), some great small but quality places, very quiet and remote.
Phi Phi another option.
You could spend a couple of nights around Kanchanaburi for jungle, elephant rides, hot springs etc, and then instead of 'last night' in BKK just leave early, takes about 2 hours.
Another option could be Krabi area and then fly from Krabi to BKK the night before your departure.

hua hin is an easy get away from bkk as is koh chang.....chang being sort of rustic and a huge national park and off shore islands to explore and a range of hotel accomodations available...

you will love both marriotts by the way, especially the phuket one...it is issolated however....we rented a car one day to get around...

Thanks for the suggestions. The empty nights are March 11-13 and yes, our flight out to Oahu on the 14th is set so we can't change that. But, we are not set to remain on the beach. I will be looking up all of your suggestions in the morning. Keeping them coming! Thanks again.