Few tourists come here opting instead only for the key temples in the Old City. It’s a real shame as outside the Old City, is where the real history and amazing ruins are. My advice would be spend one day in the Old City exploring, then a second outside at Wat Kum Aman, Wat E Kuang and surrounding ruins nearby. You can do the key ones in a day but will need either a bike or access to a vehicle as they are scattered around.

Don’t forget to wear respectful clothing (no shirt shirts or vest like tops). These are religious sites even if they are ruins and you might be denied access by tourist police if you are dressed inappropriately.