Settings>(scroll down) Device>About
Your decision should depend on where you are planning to use your GPS the most?
If you purchase the GPS in Thailand:
In case this is just one-time trip to Thailand (which is hard to believe anyway, I thought so when I came here for two months of holiday; and that was 8 years ago), I would suggest buy the unit in your country because of the reasons I mentioned above (having map updates is important, as well as the local support). If you have GARMIN you can always buy a map for Thailand (at the time of writing: 2,000 THB, approximately USD 62) or surf the web for free options, as Garmin is in my opinion the most popular GPS, there are many users willing to share their maps, tracks and POIs.
Would you agree with the above, or do you have any other pros and cons – please leave some comments.