To jump the border and go back they would probably want to charge him a fortune in duties etc as well. Each region seems to have a good place to go though. When I was in Thailand for a while (like 20 years ago now as a kid) I recall a bunch of the tech shops being sketchy even in places like Pataya. However in Bangkok there was a mall Nick named pentium plaza (don't recall it's real name) and that was pretty much the best places to get software/hardware for a computer. Ground floor was restraunts and general stores. Floor 2-3 were filled with software vendors, floor 4 was pretty much all hardware, and floor 5 was storage and stuff for the vendors.
I know there are similar places in other regions, wouldn't surprise me to find something like that in Mexico but would probably need to go to a larger city. Essentially just need to make friends with a techy person in his region as they have probably figured out those kind of locations already.