I think you'd do well with a bank account and atm card. You can actually do internet banking here. I use Kasikorn Bank and UOB. I think UOB is more progressive but Kasikorn is not far behind. I think Kasikorn has more branches. Citibank has a branch in Bangkok but nowhere else that I know of. I think that the Bank of America has an office in Bangkok.
There is an ATM booth about 2 kms away from the CVBT.