Here is an extract from the latest police order posted on AN.
See full PO here:
https://aseannow.com/applications/core/interface/file/attachment.php?id=804079
Point 6 covers the "grandfathering rules" for extensions based on retirement.
2.22 In the case of retirement:
Each permission shall be granted for no more than one year.
The alien:
(1) Must have been granted a non-immigrant visa (NON-IM).
(2) Must be 50 years of age or over.
(3) Must have evidence of having income of no less than Baht 65,000 per month: or
(4) On the filing date, the applicant must have funds deposited in a bank in Thailand of no less than Baht 800,000 for the past three months. For the first year only, the applicant must have proof of a deposit account in which said amount of funds has been maintained for no less than 60 days prior to the filing date: or
(5) Must have an annual earning and fluids deposited with a bank totaling no less than Baht 800,0000 as of the filing date.
Translated by Siam Translation for thaivisa.com. The translation of this document is for information purposes only.
(6) An alien who entered the Kingdom before October 21, 1998 and has been consecutively permitted to stay in the Kingdom for retirement shall be subject to the following criteria:
(a) Must be 60 years of age or over and have an annual fixed income with fluids maintained in a bank account for the past three months of no less than Baht 200,000 or have a monthly income of no less than Baht 20,000
(b) If less than 60 years of age but not less than 55 years of age, must have an annual fixed income with funds maintained in a bank account for the past three months of no less than Baht 500,000 or have a monthly income of no less than Baht 50,000