How long have you stayed in Thailand.
The definition of a residence certificat, is that the foreigner have stayed at least 3 month, so anything short of that, is up to a friendly Immigration Officer.
What are the reasons for wanting a Thai Bankaccount, is “nice to have”, or because you will deposit large amounts of money .
That could affect the willingness of the bank employe to open the account.
You may have had the same difficultness to open a bankaccount in your homecountry as a foreigner, so it is not specific to Thailand.
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Or use google to get the form.