First, you need to learn the difference between a visa and a stay permit
*** to get the VISA, you can show money on your HOME BANK ACCOUNT or on any bank account anywhere in the World, as long as you show the account is in your sole name. Most Thai embassies will ask for the upload of three months bank statements into the E-Visa online application.
*** If you enter Thailand on a Non-Imm O retirement VISA, you can get a Thai bank account opened on this visa class.
*** to get the “1-year extension of STAY PERMIT based on retirement, on Immigration, you either need a minimum of 800,000 THB on your THAI bank account, or an affidavit of income over a minimum of monthly 65,000 THB
*** Handle the process like hundreds before you have it done: apply and get issued the 90-days single entry Non-Imm-O retirement VISA in your own country before you wing your way to Thailand.
*** when you enter, you will get stamped in for a 90-days STAY PERMIT, and the VISA will become invalid.
*** Get TM30 registered in your accommodation, which can be a hotel or a rental apartment. Visit Immigration and ask them for a “certificate of residency” addressed to a specific bank, with the plea to get a bank account opened for you. Some banks accept if you show a long term rental contract Further, you will need a Thai mobile SIM card and number registered in your name and passport number. I recommend either Kasikorn Bank or the Siam Commercial Bank.
*** Immediately transfer a minimum of 800,000 THB to your newly opened Thai bank account.
*** Wait until the deposit has been in your account for a minimum of 2 months. Visit Immigration with the “letter of guarantee” (in Thai: rab roong thanakan) from the bank that confirms this seasoning period, and apply for the 1-year extension of temporary stay permit. Immigration calls this wrongly “visa extension”, however you do not have a visa anymore which could be “extended”. They simply extend your stay permit.
***The E-Visa fee for the 90-days Non-Imm-O Visa online application is around 80 USD.
The fee for the bank letter should be something like 200 Baht.
The fee for the application to the 1-year extension of the stay permit is 1900 Baht.
*** Don’t forget to buy a re-entry permit for your one-year stay permit, on the day you get your 1-year extension stamped.
*** if you think that this is too difficult then you can use the service of an agent to do everything for you. Using your own funds, such a service would cost around 12,000 THB.
In case you have no own funds, it will cost significantly more to get around the existing law, like up from 34,000 THB, and if you entered on a tourist visa instead on a Non-Imm visa class, you can expect an agent fee up from 60,000 THB.