This is exactly what we did in January, as our previous visas/extensions expired during Covid. 90 day O eVisa based on retirement, (UK residents, UK passport and wife German passport). eVisa applied for Sunday evening, a query received Monday and answered, and eVisas issued Tuesday. All very painless. 43 days before expiry of the 90 day, went along to Phuket Immigration and applied for, and both received, an annual extension. Straight in and out; no queue and processed together in about 15 minutes. Next day at 1pm collected our passports and another 30 minutes to get a multi-reentry stamp. In our case, we used Thai bank accounts that we already had for both the 90 day and the subsequent annual extension.
Single entry eVisa 90 day O is an A4 PDF and the entry stamp is just a standard entry stamp with the date that they gave me to stay, in this case 90 day, based on the visa.
Due to COVID, our annual extensions had expired, so we just got a 90 O eVisa outside the country (took less than 48 hours) and then last week went along to Phuket Immigration and got a 1 year extension based on retirement. Took 20 minutes. Went back next day to collect our passports and get the the multi-entry stamp. All very painless