no. 19th September is the last you can ENTER Thailand. You then get a fresh 60 days stamp.
If you would enter on last validity day, you can technically stay another 90 days. 60 says plus 1 extension. But after that need to leave Thailand.
So in your case almost until Christmas if you plan your last entry close to visa validity expiry. You essentially can get close to 9 months IF you enter Thailand shortly after the visa is issued.
For the future: 4 weeks in advance is plenty time to apply visa,
Visa validity: the timeframe you can enter Thailand borders.
Entry stamp: the last day you have to exit OR get a 30 day extension.
yeah head injuries can be serious. I feel guilty, but can help laughing at the incoherent rambling. “Pathetiktik” 😅 It has entertainment value at least