I have an O A Visa which expires in February 2021. If I am able to return to Thailand before then will I receive a one year extension when I arrive at BKK.

 

If you enter the country prior the date you visa expires you will get the one year permission to stay (it is not a extension) that it allows.

Will you have the insurance that is required when entering the country with your OA visa.

13 hours ago, Jomtien Larry said:

I have an O A Visa which expires in February 2021.

1 - Are your referring to the validity of the Non Imm O-A Visa as printed on the Visa sticker, or to the permission to stay date as stamped in your passport when you entered Thailand on that Non Imm O-A Visa?

2 - In case you are referring to the permission to stay date and the Visa validity has already expired, did your 'protect' that permission to stay by buying a Re-Entry Permit before exiting Thailand?

3 - When you applied for the Non Imm O-A Visa in your home-country, did you do this after 31 Oct 2019 (which implies you met the health-insurance requirement which was mandatory from that)?   And if so, is that original health-insurance policy still valid or did you renew it in mean time?

>> The answers to the above will clarify your situation and how to proceed from there.