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.