Will the date i start going from TVisa to Non O Visa make that in the future it will always have to be extended in the same month ?

Let me explain: Phitsanulok Immigration .

If i start TVisa to Non O Visa on 1 September i will normally get the first 3 months Non O on 22 september.

Will this mean that i will always have to be in Thailand in December to get the year extension?

Can the date be made earlier or later ?

Thanks for all the fantastic help we all get here.