Postal Service in Chiang Mai

I am hoping to retire for a few years in Chiang Mai. How reliable is the Thai Postal Service?

1. Sending letters overseas?
2. Sending packages overseas?

3. Sending letters within Thailand?
4. Sending packages within Thailand?

5. Receiving letters from overseas?
6. Receiving packages from overseas?

7. Receiving letters from within Thailand?
8. Receiving packages from within Thailand?

9. Receiving packages when ordering from Amazon?
10. Receiving packages when ordering from Ebay?

Any information about your experiences would be helpful. Having lived in Bangkok for 5 months last year, I:

A. Successfully sent letters/postcards to family in the USA.

B. Received 3 out of 4 packages from items bought on Ebay. I may have left Bangkok before the 4th got there, so I can't blame the Thai Postal Service on this one miss.

Any info would be appreciated.

Well, looks like you have had as much experience with the mail in Bangkok as I have in CM (without a hitch btw), so I'm not sure how much I can help, especially since I've never lived in Bangkok. But I will say that it's important and worthwhile to find out exactly what your address is, and exactly how it's supposed to be presented on any package or letter.