Postage Overseas,not From The Big Cities

what do you think about the reliability of thai post,& shipping options (couriers) for regular,very small,quite valuable packages to the uk,usa etc,if i wanted to stay out the way abit,eg issan.

i see fed ex has offices in bkk,chiang mai,chonburi,but what about further afield,are their sub offices reliable?

i'm looking to stay in an area of thailand thats not too touristy,& not to much pollution,noise etc,& somewhere i havent stayed long term before.i was initially thinking about the outskirts of chiang mai.