I stayed at the Anantara a couple of months back and overall had a really excellent stay. We had considered the FS but wanted to do more things in Chiang Mai itself and it's wildly inconvenient for that. Overall I wouldn't say the Anantara was to the level of a Four Seasons/MO/Peninsula but it was maybe half a notch down.

We had some minor issues but they were resolved extremely well. We were in a Deluxe River View Room and on the first day, early in the evening, the room started to get a strong paint smell. We alerted the front desk who tried to resolve it whilst we were out for the evening but the smell remained when we came back, so they upgraded us to a Kasara River View Suite for the duration of our 4 night stay.

We ate at the 1921 Restaurant one night and the food was excellent, breakfast was a huge selection and of really good quality out by the river, lovely and relaxing. We used the spa a couple of times and found the treatments to be really decent too, although prices are obviously much higher than you can spend by venturing outside the hotel. (We had a free treatment through Virtuoso and then got offered a heavily discounted rate for a second treatment). Even tried the cooking school which was a really fun experience with a tour of the market where we bought the food we were to cook but also the chefs allowed us to try anything we wanted, or there recommendations, free of charge which was a fun element to that.

The location is just right, IMO, you're just a couple of minutes by tuk-tuk from the Old City so close enough to everything but by the river and away from it when you want to relax. Staff were also faultless too.

IMO, you could almost do a couple of days at the FS then a couple at the Anantara.