I have an extended stay retirement visa which expires in November. I will be in a foreign country during that expiration date and must return to Thailand to renew the extension. When I return to Bangkok, must I go to the Immigration office that issued the extended stay visa or could I just  go to the main Immigration office in Bangkok and renew it there?

If you are registrered as living still at the same place, you should go to the immigration-office who performed this extension of stay based on retirement (NOT A VISA).....

 

glegolo

59 minutes ago, thailen said:

I have an extended stay retirement visa which expires in November.

I assume you plan on returning before it expires. If you enter after the date it expires you will have to start all over again to get a new extension of stay.

1 hour ago, thailen said:

When I return to Bangkok, must I go to the Immigration office that issued the extended stay visa or could I just  go to the main Immigration office in Bangkok and renew it there?

You must use the office where you got your current extension of stay (not a visa) unless you formally change your address to another office.

Is your "extended stay retirement visa" an "O-A Visa" obtained at a consulate in your passport-country?  If so, you can leave and return to Thailand before the "Enter Before" date printed on the visa itself, and get another year "permitted stay" stamp from the date of that entry.  You must then get a re-entry permit to keep that "permitted-stay" alive, if the Visa will expire ("Enter Before" date) before your return.

 

If what you have now is not an "O-A Visa" - but is a 1-year "extension of stay" obtained at an immigration office in Thailand, you would need to renew your extension before it expires, then get a re-entry permit for that extension, to avoid starting the process over from scratch when you leave and return to Thailand.