If you plan to overstay just remember if you get pulled up anywhere even on your way to airport . You'll be in big trouble . Is it really worth the risk for a 1900baht extension that you can get?
You can probably go back to immigration on the 25th January ( In which the covid extension ceases for now ) and get another covid extension and pay 1900baht instead of taking the risk
It took you 2 weeks to reply.. However you may be allowed to enter Thailand being positive but are you allowed to board the airline with the same result?? .
So is that a risk you are willing to take .... Good luck with it all ....