Take a overnight train from Bangkok to Chiang Mai, a very comfortable train reaches chiang mai early in the morning.. You find plenty hotel/ guest house representative wiling to provide you their services at railway station itself..choose any as per your budget..
An old Buddhist Monastery on the outskirts of town, you can hire a Tuk-Tuk or any other local transport to get there..
The peaceful ambiance and lovely decor of temple is mesmerizing, spent some time roaming around.. You may happen to bump these little girls dressed in tradition attire and take pictures with them, though language is a barrier but you can still enjoy communicating to them..
There many handicraft shops to pick lovely Thai stuff .. Come to town and spey you evening surfing around night markets or pubs..
Almost every hotel has tie ups with these tour company's and ready to provide you Travel/ Adventure tours at competitive prices..choose from vast list of "Elephant farms/ Quad Biking/ longest Zip line/ White River Rafting and may more.. The most recommended is take "Day Tour to Chain Rai" Witness the beauty and intricate artwork of "White Temple" at Chiang Mai, it seems heavenly, Then visit "Golden Triangle" where Mekong river joint the border of three countries Burma, Thailand & Laos..get a quick land visa through you tour guide and step on Loas land buy for some real good shopping.. Later take a visit to Northern Karen tribe village, these people are mostly immigrants from Burma and commonly know as Long Neck tribe..The female members of tribe wear rings around there neck to make it long which symbolizes beauty in their tradition.. Come back to town after a quite busy day and hang around in Night Markets for inexpensive shopping and mouth watering food stalls..
Take a day to spent time on adventurous activities..choose any from the various packages..and just go for it..