While you're in Thailand, be sure to escape the colorful chaos of Bangkok and head toward the historic capital of Ayutthaya, a UNESCO World Heritage site.
The best option to get there would be by train and they run frequently from Bangkok's central station and take just over two hours.
Upon arrival you'll have tuk tuk drivers and bike rental salesmen fighting for your services and either way are a great way to get around and explore on your own time. If you're short on time, I'd suggest the tuk tuk, but a day biking among the ruins of this ancient city is hard to beat.
Ayutthaya is a ghostly city of beautiful ruins and entangled or slanted wats. Brightly colored offerings are gorgeous contrasts to the aging stones and brick. King Ramathibodi founded Ayutthaya in 1350 and city was the capitol of the Siamese kingdom until its destruction by the Burmese army in 1767.
Leave Bangkok behind and go and make this exceptional place, yours for the day. Be sure to grab a map and some bottled water before you start navigating the treasures.