This monument has a relatively massive courtyard in front of the statue that honors the founders of the walled city of Chiang Mai.
It is kept clean there and it is a very important part of the city's history, however that is kind of where it ends. This is actually part of a day walking tour that can be done to visit all of the historically important aspects of the city but to be honest you could really skip this one because after you have taken a photo and read the plaque, you are pretty much done and you aren't going to remember what is written about the history anyway :)
I would say that it is better to visit it at night because there is virtually no shade because there is no shade at all in the courtyard (or any courtyards for the most part) and Thailand is hot, even in the north.
If you can manage to make it on a Sunday night that would probably be the best because there is a cultural market that takes place in the courtyard as well as a blocked off street nearby with lots of stuff to eat and perhaps make a purchase of a souvenir or two.
Mostly, I would suggest that you don't really need to go to this at all, especially if you time in Chiang Mai is limited. However, if you are staying in the city center (inside the walled city) you may as well because everything is relatively close together.