For some reason I cannot connect to the internet with my HTC desire with my 12 call sim, however if I put the sim into my samsung, I can get a gprs internet connection. I can connect to wifi no problem, but its when I am out and need to check emails etc. I have looked at the settings , and I think I have checked all the correct boxes, but maybe I am missing something, or indeed need to download an app,

any advise please techies

I think you just have to set up the APN?

http://www.ais.co.th/faq/th/handset_setting.html

(Use Google translate)