Do not go to Thailand and stay at the mammoth hotels frequented by Russians.
Three days is enough for Bangkok. Sleazy as well as mad. Stay at the Oriental or directly across the river at the Peninsula (however, both well over $200 but well worth it).
For a beach, Krabi is good; however, Koh Phi Phi and Koh Lanta are better. $150-180 is more than you need for 4 stars. The beaches are not crowded as in Phuket, and there are daily excursions to some idyllic beaches at National Parks, emerald cave, etc.
If you wish for more remote, look north of Phukett. Jungle trekking and all-day trips to off-shore dive sites. Beaches are okay.
http://www.similanaresort.com/rate.htmlIf you are a wild man, and if there is a full moon, go east of the peninsula and stay at combination of Koh Phangan. The only problem are mobs of backpackers. There is a 4-star resort there for about $100 where you can escape from the young 20s set. Fabulous outdoor restaurant setting. You can get island fever on Koh Phangan in a few days because there is so little to do.
http://www.panviman.com/phangan/index.htmlI enjoyed a 4-day side trip to Laos. It was a far closer experience with the people and their culture.