I saw some discussion about this in threads from a year or two ago, but knowing how often things change here I figured better get a fresh discussion going.

My contract ends on, oh let's say March 13. I'm peering into my crystal ball and I don't see myself renewing it when the time comes. I understand from other threads that if I were to leave before the end of the contract, I'd need to visit both labor and immigration to get the WP & extension cancelled.

However, since I'll be finishing the contract and not renewing, there'll be no need for me to go to labor, correct? In other words, just let the WP expire; no need to cancel it.

Next question: Can I go to immigration on the 13th and get switched over to an extension based on retirement? IOW, can the retirement extension be applied for and granted the same day my B extension expires, or will I need to plunk down the 1900 baht for an extra seven days while I'm waiting for some kind of review/consideration/approval period? Let's assume I've got all the paperwork, proof of funds & address on hand. As long as I'm prepared, can the switch from B to O happen in a single visit to immigration?

Thanks.

There is no consideration period for retirement extensions. If all is good you will have it immediately.

You will on an extension of stay as possibly you are already, not on a non-imm 'O' visa. There is no 'visa switch'.

Yes I'm on a B extension. I was careful not to use the word 'visa' in my OP because I realize I'm on an extension. Anyway that's good to know.

When you're on extension the category is give by the numbering in the regulation, e.g. you will change from 2.1 to 2.22

When on a visa, non-immigrant is the type, and 'O', 'B', or ED etc the category.

There is no straight mapping between the two things.

You will be able to change the reason for your extension from working to retirement. You will need a letter stating you are no longer working so that immigration can cancel your extension and issue you a new one for retirement.

You will need to meet the financial requirements for retirement on that date.

Yes I'm on a B extension. I was careful not to use the word 'visa' in my OP because I realize I'm on an extension. Anyway that's good to know.

"I was careful not to use the word 'visa' in my OP"

But you referred to switch from B to O and state you're on a B extension. Non-Imm B and Non-Imm O are visas. You may want to change the basis for your extension of stay, but switching from B to O implies you want to switch visas.

WP does not need to be canceled if the WP expires on your last day of employment. If the contract expires but the WP is still valid till after that date you would need to cancel the WP.

To follow up on this - I just noticed my WP and extension are both valid through the 14th of next year - that's a Saturday. If I go to immigration on the 13th to switch over to a retirement extension, would they do it seeing that my WP was technically still valid for one more day, or would they make me go to labor to officially cancel it? Seems silly, but I don't put anything past the bureaucracy.

And if the answer is yes, then the next logical question is - how many days in advance of my expiration dates can I visit immigration and do the conversion without having to cancel my WP?

You can apply in the 30 days before expiration. Money needs to have been in the bank for 2 months.