I guess Pete might return directly to Chiang Mai by air. Please don't take this as definitive, but in trying to get a ballpark guidance from from someone we know related to CM immigration they are ideally looking for 4-5 months per year for tourism, eg. one SETV and one land border, both extended. Obviously they are not implementing this strict, but this is what I have heard would be fairly reliable long term, since I'm not yet 50.