The 7100, 7105, 7130c, 7290 or 8700 will work fine there.
However, with a local (Thai) SIM card, all you will most likely get is voice and SMS text. Unless you can find a local carrier with a BlackBerry Data Plan, you will be out of luck.
Without a BlackBerry Data Plan on the acoxxxx/SIM, the BB will be limited. You may want to investigate a GSM/GPRS phone which can do your GMail.