What is required for an Income Certificate for a Retirement Visa in Thailand?

Okay. You using Bangkok Bank makes it easy, as I use the same bank and now use the monthly income from overseas transfers.

At the main offices of Bangkok Bank on SiLom road go to the counter on the far right in the bottom floor. They will process your confirmation of having a bank account with them, and it takes a few days. When you get this confirmation you take it to the second floor up the escalator and into the first offices on the right and to the first desk. They will gather all your monthly deposit records for the last year, and print them for you. These are what you need at immigration showing all your monthly deposits coming from overseas for the last 12 months. This again takes a few days. The total cost for all this is about bt800. The records you have access to with online banking only covers the last three months, so you can not do it yourself. These two things are what you need. The letter certifying it is your account in your name only, then all these deposit records showing them coming from overseas, and the exchange rate used, and deposit in baht. It is a stack of papers. This is how it is done with Bangkok Bank. Then there is the copies of your bank book and updated on the day you apply. This can be done doing a small withdrawal or deposit then updating your bank book at the ATM machines at immigration.

From your profile it appears you’re from the UK. The UK embassy won’t issue income certificates. You either have the option of transferring 65k+ per month from overseas for the past 12 months or showing 800k in the bank 2 months prior to application and 3 months after and the balance not going below 400k for the rest of the year. It would need to be topped back up to 800k 2 months prior to your next application.