POSTAL

Thailand’s postal system is very reliable and quite fast, albeit not cheap for air mail to the US or Europe.
For post cards,  the local post office is just fine.

(During the research of this guide, the post office was used to send home dive suits, regulators,
books and some extra clothes, all arriving intact in the US in less than 10 days.)

Thailand also has DHL, FedEx and UPS offices, based in Bangkok. Call to find out where the closest satellite office is.
Rely on FedEx or DHL if you are sending anything valuable that requires tracking or time-sensitive delivery.