Please can someone give me the definitive address in Bangkok where I can extend my retirement visa, Thanks in anticipation.

http://bangkok.immigration.go.th/en/location1.html

Note that you only use Bangkok if you live in Bangkok. If you live elsewhere you need to use your local office.

I find the patience of tv helpful experts like the two above amazing. No offense OP but if you Google Bangkok immigration, not only would you have the address but blow by blow instructions how to get there and what to do once your there. Prob even mention free shuttle from main drag to front door.