You’ll need a long term visa to open a bank account now, ore else it’s almost impossible. An agent will manage for you anyway if you have minimum 15 days left on your current stamp. (Fee from 3500 baht). I’ve helped several people with this. (But I’m not in any way related to any agents).
Crazy, but you’ll need to marry first to get this option. The fee is 2000 baht for the 90 Non O visa and 1900 baht for the year extension of stay. You’ll need 400K baht in your bank account to apply and 400K baht seasoned for two months for the one year extension of stay.
You’ll need to check your e-visa and see if it says Non Immigrant O or Tourist TR.
If you mistakenly applied for a 60 days Tourist visa valid for 90 days -as several people have done lately- you’ll need to apply for a 90 days Non O visa in Thailand first and get an agent to assist you with opening a bank account.
If you work remotely outside Thailand and would like to stay for a year in Bangkok without doing border bounces, which probably wouldn’t give you a year anyway, your best option might be to apply for a DTV. (Destination Thailand Visa)
You’ll need to apply outside Thailand and most countries except Indonesia do e-visa now. This means you’ll need to show up in person and apply in Jakarta. I don’t think you can apply in Bali.
in any currency equal to 20K baht. This is rarely checked in the immigration (especially regarding western tourists), most important is onward ticket and up to a week accommodation if asked.
You have one month to open a bank account and bank the required 800K baht to apply for your first year extension of stay within two months. (As it has to be seasoned for two months).
If you plan to enter on 60 days visa exemption be aware of that an onward ticket out within 60 days is required for each entry even though you plan to apply for an extension at your local immigration.