I am pretty sure that model is unlocked and can accept a 3rd party nano SIM.
Normally the phone can automatically configure the necessary APN, you may have to re-start it.
But if you have to manually configure an APN; each provider's settings are different.
You may also have to manually select the APN, enable, then re-start the phone.
You could mess around with a $5 T-Mo SIM to get a feel for what it's like.
You can Google the APN settings for the three major providers here: AIS, DTAC and TrueMove H.
http://help.mobiletopup.com/article-...3g4g-and-wifi/
But there are few tricky settings (APN type: default,supl); I have all three set-up.
And any shop may be able to assist you.
If you have a certain provider in mind just let me know and I'll get the APN details. And if you have problems once here just PM me.
BTW, I just tumbled across these AIS mobile data packages which do represent a significant value. But they are one-time only packages, with hardcaps.
http://www.ais.co.th/one-2-call/en/p...x?type=1&id=44
Scroll down to Internat Max Speed valid for 5 or 7 days. 5 GB/5 days/125 baht.
There is an AIS shop in the Siam BTS station, ticketing mezzanine level, "air-side", which is always empty.