Apply for the Non Immigrant O visa based on having Thai child before you make your way into Thailand. No hassle with flights and visa exempt entry.

Get 90 days on entry and apply for the 60 days extension to visit family. Use the visa designed for this situation.

I have no idea where in Thailand the OP is going to live, but I know for sure that he can go after 45 days, they will inform him to make all needed copies and let him apply or inform him he has to wait a few more days and make an appointment to get thins done on the easy way.

Get the Non Immigrant O visa before you travel, get stamped in for 90 days and after 45 days visit Immigration to apply for the 1 year Extension of Stay. Less visits to Immigration and less hassle.

Single Entry Tourist Visa gives 60 days, once the extension is an extra 30 days, than conversion to Non Immigrant O gives an extra 90 days, yes easy to do if you can meet the requirements.

No insurance needed, no police checks, no funds transfers, just get 90 days on entry and before these 90 days ends, make a border run to get another 90 days.

Live can be easy if you look at all the options:

I would say YES, as it is mentioned on the Extension of Stay stamp, ask your local Immigration Office and please let us know the outcome.

There is no rule that short time visa or short time Extension of Stay are exempt from a re-entry permit.

@Pinky *****

Correct, you have to 18 Sep to collect new documents to apply for a new visa at a Thai Embassy. Check their websites for all needed documents and prepare with your new employer before you travel.

@Reny ***

You can but not based on being over 50 years of age, you may try based on volunteer work, being married to a Thai, depending on partner with long stay etc. The O stand for Others and not only as some people like to say retirement.

And choose Multiple Entries

There are 2 (two) different things.

a Visa which gives you 90 days of stay and can be obtained from an Embassy or as in this case inside Thailand by conversion.

an Extension of Stay for 1 year based on employment.

The 90 days you get using a Visa can not be cancelled if you do not work or stop working, you can stay until the last day of the 90 day period.

an 1 year Extension of Stay must be cancelled when the reason why you have this Extension change, like you get 1 year to work but you stop working.

As Lloyd already showed, this visa is based on working with mentioned school, you have to talk to your new employer, get all the documents ready to apply for a NEW Non Immigrant B visa at a Thai Embassy. Use that new visa to enter Thailand, pick up your new work permit and you are good to go work.