What I need to get my head around I think, is do you close the O-A and then apply for an O or a 90 day visa and then apply for the Marraige visa.

Sorry I know the question is very messy but I over think some things, mainly those to do with my continued stay in Thailand, so if you can make heads or tails of it, any setting me on the right path would be greatly appreciated.

You would change the reason for your extension of the stay from a OA visa based upon retirement to one based upon marriage.

When you do the change the reason you new extension will start from the day it is done. Best not to do it very early.

24 minutes ago, Billy Bloggs said:

What I need to get my head around I think, is do you close the O-A and then apply for an O or a 90 day visa and then apply for the Marraige visa.

You don't need to "close the non O-A"

Some unmarried guys "kill off" the non O-A due to insurance requirement and then obtain a non O as you mentioned...

 

The thing is being married you can change your reason for extension from retirement to based on marriage.

Then insurance is not required for extension. 

I did this just last week, on my application form the T7,  under reason for extension I put marriage to a Thai national and then supplied a mountain of paperwork. A few hiccups along the way as to be expected but all sorted and now waiting on application approved. 

Thats exactly what I dont want to do, cant stand having to lock a big amount away for various times and I like to have sensible insurance not some that has been put in place for no good reason.

29 minutes ago, Billy Bloggs said:

Thats exactly what I dont want to do, cant stand having to lock a big amount away for various times and I like to have sensible insurance not some that has been put in place for no good reason.

The choice between a non O based on marriage and extentions VS based on retirement and extensions had nothing to do with insurance.

Insurance is not required. 

Agree the financials are very different for the two options.

What also needs to be factored in is the non financial requirements.

Retirement very simple compared to marriage.

Many married guys choose retirement extensions for that reason.