Do I need to check my bank balance at immigration 3 months after my extension in Bangkok?

When you were sitting at the desk of the I/O getting your extension they had you sign several papers (acknowledging overstay penalties, agreeing to contact them if the reason you got your extension changed, AND agreeing to the terms and conditions of your extension).

Chaengwattana does not hand out a paper stating you come back 3 months after you get your extension, they will check the bank balance when you get your next extension to make sure you kept the balance at 800K baht for 3 months after your extension was granted and that the balance never went below 400K for the rest of the year.

Thanks for your good question Fabio...

And as its nightime in Thailand,

@Tod ********

will reply in the morning. Thank you for your patience.

I do not believe Bangkok CW office is asking for proof in 90 days of the 800,000 Thai baht bank balance.

And as you stated...

From reports not all immigration offices are requiring a person on extension of stay for retirement to return at 90 days to show bank book balance of 800,000 Thai baht.

Regardless ...all persons who receive the one year extension of stay based on retirement are required to maintain the financial requirements of your stay...

Which means its your responsibility to maintain a bank balance of 800,000 Thai baht during the first 90 days ...and that the balance shall not go below 400,000 Thai baht at any time during the year, and that you show a balance of 800,000 Thai baht during the two months before a new renewal if your extension of stay.

Failure to meet those requirements may mean cancellation of your permission of stay when you seek renewal.