Dont think these have been posted before...
DTAC
APN: mms
Username: "NA"
Password: "NA"
MMSC: http://mms.dtac.co.th:8002/
Proxy: 203.155.200.133:8080
AIS
APN: multimedia
Username: "NA"
Password: "NA"
MMSC: mms.mobilelife.co.th
Proxy: 203.170.229.34:8080
TRUE
APN: mms
Username = true
Password = true
MMSC: http://mms.trueworld.net:8002/
Proxy: 10.4.7.39:9201
Now for sure that the Dtac settings work. The others are from Thai forums and have not been tested. Just my little contribution