Please help me with this visa problem:

I will enter Thailand on a tourist visa in October and marry in November before applying for a spousal visa.

The marriage visa requirements stipulate that 400,000 THB must sit in a Thai bank account for two months prior to the visa application.

Last time I tried to open a bank account in Bangkok on a tourist visa I was turned away at three different banks.

Is there a way to open a bank account on a tourist visa, or am I missing something? (Might seem like a simple question but I haven't had any luck finding the answer)

Thanks very much