Can anybody please tell me if I'll need anything different than this?

Passport (and signed copies each page)

Departure Card TM (and signed copy of it)

Thai Bank Book 800,000 baht (and signed copy of it)

Letter from Thai Bank - 7 days advance

Deposit 100 baht into Thai bank account

Copy of proof of address

Three (1) 4×5 cm photos

Completed application TM-7

1900 baht

How many days in advance does the 100 baht have to be deposited into the bank account? It takes 3 days for the bank to write the letter.

Thank you.

I just found this on the Samut Prakan immigration website. It seems to me that much more then this must be required - am I wrong?

http://www.samutprakanimmigration.go.th/list-of-documents-for-retirement-visa/

List of documents for Retirement Visa

1. Visa Extension Form (TM.7)
2. Passport or Travel Documents
3. Non-Immigrant Visa
4. Letter from Thai Bank certified money in Thai account more than 800,000 Baht 3 months before and ATM slip on date of application OR
5. Income or Pension have to certified by The Embassy or Consulate in Thailand and show income more than 65,000 Baht/month

I have to do this in the coming month but I can't understand why you need to put 100 baht into the Thai bank account.

What is this 100 baht for?

To update your bank book to show them the money is still there.

I get my passbook updated at an ATM type machine outside the bank. Is this not sufficient?

I get my passbook updated at an ATM type machine outside the bank. Is this not sufficient?

Yes. My bank will update my bank book at an ATM too and the bank manager always updates it before writing the letter anyway.

Some banks only update when you make a transaction. As long as you do a machine update on the same day you get the manager's letter and the balances are exactly the same in the book and in the letter, that's all you need.