Unfortunately, you need your bank account BEFORE you apply for an in-country Non-O visa based on being over 50 at the local immigration office.
Bangkok doesn't require you to have your funds seasoned for in-country initial Non-O visa application. You can apply for a visa next day of your deposit. Two months of seasoning is the requirement for a 1-year extension application when you already Non-O (90 days) stamp.
Bangkok requires you to have a lease agreement for application for an in-country visa and following 1-year extension
Attachment is the rough process for visa and extension applications all inside Thailand.
This is the requirement list for an initial in-country Non-O visa based on being over 50. But you need to get the latest one at the CW office.
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