If you need to mail a postcard or a parcel in Chiang Mai, Thailand, there are two helpful places in the Maya Lifestyle Shopping Center in town.
Mailing A Post Card In Chiang Mai
On the 3rd floor of Maya there is an awesome little book shop called Asia Books. These guys will sell you stamps for your postcard as well as mail the postcard for you! Postcards in Thailand are around 15 – 20 Baht (£0.30 – £0.40) and at Asia Books, 3 stamps to mail postcards internationally costs 60 baht (£1.20).
Mailing A Parcel In Chiang Mai
If you ever need to post something substantial back home there is a Mail Boxes Etc. on floor B1 (down in the basement) where you can post things via UPS. It felt extremely expensive though, circa 1500 Baht (£30) to post the tiniest thing back to the UK, via UPS Air Mail, which will take 1 week.