I have a 1 year retirement visa expiring at the end of March 2016. I need to return to Australia just prior to the expiry date and return about the 2nd. week in April 2016. What is the outcome that my visa has expired and will I be given time when returned to re-new my retirement visa?

What "visa" do you have and where was it obtained ? .

There is no "retirement" visa !

extension of stay based on retirement I believe it is called, in Chiang Mai

There is no retirement visa. If you arrive in Thailand with any type of visa after the "enter before" date stated on the visa, this visa is no longer valid.

You should apply for another one year extension of stay before you return to Austrailia. Once you have a new extension of stay you would need to get a re-entry permit also.

If you don't get a new extension before leaving then no need for a re-entry permit because it would only be good until March 2016.

This is assuming that this is not about a visa and that you really have a one year extension of stay (retirement)

You should apply for another one year extension of stay before you return to Austrailia. Once you have a new extension of stay you would need to get a re-entry permit also.

If you don't get a new extension before leaving then no need for a re-entry permit because it would only be good until March 2016.

This is assuming that this is not about a visa and that you really have a one year extension of stay (retirement)

You can apply for another one-year extension of stay up to 30 days before your existing extension expires. Indeed, this can be done up to 45 days beforehand at some immigration offices - although I'm not sure whether Chiang Mai are one of these.

But it it's really another visa that you're after (visas cannot be renewed, only replaced), then why not simply get a fresh non-O while you're back in Australia?

I have a 1 year retirement visa expiring at the end of March 2016. I need to return to Australia just prior to the expiry date and return about the 2nd. week in April 2016.

Apparently you have an extension of stay, not a visa. Apply for a new extension before you leave. After you get the new extension, get a new re-entry permit that will be valid for the length of your new one year extension (or until it's used if it's a single re-entry).

If you return after your permission to stay ends without getting a new one, you will have nothing other than a visa exempt entry. You'd need a new non-imm O entry and then need to make a new extension application during the last 30 days of the non-imm O entry.

Far better to get the new extension and re-entry permit before you leave for Australia. You can return to Thailand any time during your new one year extension of stay as long as you also have a valid re-entry permit.

Thanks for all the replies and very helpful, cheers