Welcome to Chiang Mai.

Northern Thailand is a world away from the bustle of Bangkok or the crowded beaches of Phuket. You come here to enjoy the temples, cooler weather, and mountains.

This section of the country offers many different experiences. Your trip's length can be planned using the day-long building blocks as a guide :
i) a full day exploring the historic city centre and its many temples
ii) an overflow day for more temples inside and outside the city walls
iii) squeeze in one or two night markets after your day's sightseeing
iv) Doi Suthep, the mountain closest to the city
v) excursion to either an elephant orphange or Doi Inthanon

You should also consider Chiang Rai, but not as a day trip. That town is quite a distance away and you will need at least 3 days to properly cover the temples and Golden Triangle.