I intend on applying for a Non O 90 day visa in the UK. This will be based on being married to a Thai spouse.

I have a Thai bank account with ฿500,000 for over 3 months for the purpose of extending for 1 year.

I am not able to stay in Thailand for the whole 90 days and will obtain a re entry permit to keep the visa live.

My question is regarding the under consideration period required for the yearly extension.

If I return to Thailand a couple of weeks before the initial 90 day period is due to expire will this be sufficient to allow the extension.Or because of the under consideration period taking me past the permission stay stamp into my passport when I re enter Thailand it will not be viable?

Apply any time up to the end of your 90 day entry. The "under consideration" time is bonus time for you, although the eventual extension will still have the same start date. But during the under consideration period you are entitled to stay in Thailand.

33 minutes ago, mlkik said:

If I return to Thailand a couple of weeks before the initial 90 day period is due to expire will this be sufficient to allow the extension.

As already posted above... for extension you can apply anytime up to expiry of the 90 day stamp.

Some people get confused after reading that you must apply 15/21 days prior to expiry of a tourist visa or visa, exempt entry.

That requirement is for obtaining a Non O inside of Thailand at local immigration office.

You will be obtaining the Non O in the UK on eVisa platform (good move)

Just obtain the extension after you return to Thailand.

You can obtain reentry permit at local immigration or airport.

You do not go into overstay during under consideration period.