Okay most answers covered your situation.

Could you not also:

Instead of applying for the 1yr extension, apply for 60 day visit Thai family extension and get a reentry permit (always).

Then when you return from your trip apply for the 1 yr extension.

It buys you 60 days "in a sort of Limbo" status.

Many use this 60 days to get money in order etc. for the extension.

You only have to do a 90 day report if you have a "longstay" extension of your original visa or 1yr. visa like an OA.

Address registration all foreigner must have within 24hrs of arrival , known as TM30.

@Brandon ***********

guardian is 500k.

Yes technically all foreign Nationals have to have their address registration within 24 hours of arrival.

It's called a tm30, if you are in a hotel it is usually done for you.

If you will just be leaving the country after 60 days, it likely won't matter if you are registered or not.

If for some reason you are staying longer, you may run into problems if it is not done.

You can purchase a disposable policy from an approved thai carrier.

Disposable as in covers nearly nothing but meets the Thai requirements.

Not ideal but a work around if you have coverage that doesn't qualify for whatever reason.

Many of us have already learned "why" is a waste of energy.

DO or DO NOT there is no "why"

It would be super helpful to post your location, that maybe someone can give you accurate info.

Otherwise go to your local immigration office for the specifics.

If you fail to plan;

you plan to fail.

Are we assuming the 90 is really 30 and just a typo.

Other than that yes that will work.

BUT YOU CAN manipulate the system.

When you are expiring go and apply for a 60 day visit family extension ( this assumes you haven't used one recently) , then go back during that 60 day and apply for the extension.

Then you don't have to leave.

Speak to your local immigration office, an agent is not necessary unless there are other issues.

If asked why you are doing that , you can say you need time to season your funds for 2 mths. To meet the criteria.

Phuket immigration is 45 days