won't make any difference at all there are over 80 immigration offices in the country and you can get a 30 day extension on a free 45 day visa exempt entry at all of them
Most allow you to apply when you have 30 days or less left on your stamp
If you're going to get it in Chiang Mai before you travel use the Central Festival Mall immigration office <- it is NEVER busy and you'll be in and out FAST
It's here
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