Thai post office inside of BKK airport on the far right end of departures floor. Open from 12:15am-23:30pm everyday. Very cheap to ship. In May I shipped 20kg worth of things to Chiang Rai for only 400 baht and got it the next day.
I have a non-o spouse and I have a WP, it certainly is possible. Go this route because as Steven said above 👆, if you lose your job for some reason, your visa is cancelled.