If I work in Bang saen and have all the documents to process my ext of stay but dont have time to do it at the local immigration office today can I do it on holidays down in Phuket. Are there any rules in this regard?

thanks

You can only apply for extensions of stay at the designated office for where you are living.

Only where you are living.

I live in Samut Prakan, work in Bangkok. I have for years been doing my yearly extensions in Bangkok (Chaeng Wattana), so in some cases no, it doesn't have to be where you live.

Yes. It has to be the office that covers the area in which you live.

You will have to provide proof of address .

I live in Samut Prakan, work in Bangkok. I have for years been doing my yearly extensions in Bangkok (Chaeng Wattana), so in some cases no, it doesn't have to be where you live.

If working you do need to do it where you are working since that is where your work permit is issued. That is an exception to the rule.