As stated my first 90 days are coming to an end early October (date of permitted stay stamped in Passport) for my Non Immigrant type O multiple entry visa ( Visa will expire next year ) . I am married with a Thai wife.

From reading various blogs I see that I can apply for a 90 day Extension rather than leave the country? I can then repeat this process up till the visa expiry?.

Can someone please confirm my understanding is this correct?.

At the end if the visa next year I can then apply for a 1yr Thai Spouse Visa.

I do not know where you read that but it is totally false. You must depart Thailand and return for a new 90 day stay. Alternative would be a 60 day extension from immigration with wife/her ID/Home register or one year extension of stay by meeting financial conditions of 400k in you name bank account here for 2 months or having 40k per month income here with tax payments or outside Thailand with letter of such from your Embassy.

There is no such thing as a spouse visa - what you have is what you get for marriage - what you are thinking about is the one year extension of stay I mentioned above and you can apply for that during the last 30 days of any non immigrant O visa entry - you do not have to wait until visa expires.

Thanks Lopburi3, I will probably go for the 60day extension does this come with a 1900bht price tag that people are mentioning?. I have most of my funds in banks aboard.

We are going to move down south to Hua Hin and will go to the immigration dept there for the next check in. Any problems besides the blue book that you can enlighten me on?

Yes all extensions of stay are 1,900 baht.

There is no next immigration check-in required until you are ready to extend for a year. For a new 90 day entry you must exit the country and return.

However, OP needs to submit a change of address. Hua Hin immigration has been reported as one of the offices that observe this requirement.

Hua Hin was asking for that of persons requesting them to provide a certificate of address. He should not need to report address changes when on visa entry of 90 days or less.