hi, I had used a matrix sim card for Thailand for almost 5 days. I found the network coverage to be very good. Atleast it was better than what my friends were using there – a pre paid sim card they purchased locally. Local calling was very cheap and calling back home in kerela wasn’t too expensive either. Overall I had a fairly decent experience using matrix sim card. Infact my friends who experienced issues with their local sims landed up using my sim as well for a few of their calls.