Only real long term visa have a slight chance to open a Thai Bankaccount, if they have a permanent adress on a long lease, a easy controllable moneyflow in and out of the account
Like most other countrys, tourist are not able to open a bankaccount, and DTV is a touristvisa, given to nomads that by definition are moving around frequently.
Banks in Thailand are like everywhere in the world, interested in having good stable custormers, that have a permanent address, a steady easy traceable income, and use the account all year round.
That is why the banks are reluctant to give accounts to people on short time ( read: tourist ) visas, and who only spend part of the year in Thailand.
Don’t expect to get a residence certificat, until you have stayed at a permanent adress in at least 3 month, since that is what the residence certificat should confirm.
Furthermore the added attention on whitewashing of money, is an added burden on the banks, so reluctant depositing large amounts isn’t a guaranteed way to open an account.
The value of a resident certificat, had gone down, since Immigration Officers are giving them to people that are not on a longterm visa, or have stayed severel months at 1 adress in Thailand, so even if it is a formal requirement, the bank make up their own assesment of the stability of the want-to-be customer.
DTV is not for language schools, there you should go for a ED visa, if trying to get language on DTV, Embassies give a ED visa or reject, and keep all the 10.000 baht DTV visa fee.
Only apply for ED if you really want to be a fulltime student, or you may end up in troubles.