Since IOs been overwhelmed it seems they process after hours/overnight and let people return next day office is open If you got s token to collect and paid and paper approved and not had a Non Immigrant visa before C extension you most likely fine. But still up to the IO ✨
you asking about borderrun. Technically you can get out, back in on a 30 day Tourist Exemption (if your passport allows) and thereafter apply for tourist 30 day extension. By then COVID scheme expired. Maybe beter to come back on a 60 day visa, and then extend to 90.
Atm there are no 1 day border runs, one needs to do at least Thai pass and Test & Go to get back in ✈️ no landborders are open.
Officially you need a big Motorbike over 50(?)cc license. An international does the trick when getting stopped to avoid a fine, but you not insured if any accident. Only having the correct motorbike license + an international does.
In cities fines are more a thing then in country-side or some islands. They even put up roadblock funnels to catch mostly non-Thai.
It's possible to get through the process of a Thai license with some tests that covers car/bike.
In case you go volunteer you need a proper volunteer visa, not allowed otherwise as a tourist (though people do 🙈) Showing a letter like this is not helpful in your case, and might bring up other issues.