The OA visa is more difficult to get. And always needs a full health insurance. NON O is still without the demand for insurance when you make a yearly extension.

Its a commonly used option. Maybe you go to your local immigration and ask for their procedure to show the monthly transfer. Individual immigration offices tend to have different procedures. Which immigration office are you planning to go to? Maybe some one can tell his/her experiance there.

I guess you came back on a visa exemption. VOA is for limited number of countries and only 15 days

I would never wait untill the last days. You never know what happens. Better have the extension secured.

Actually it enforced as the time passing the departure immigration. A flight shorty after midnight is no problem.

Immigration FAQ's

Q: We need to extend our stay in Thailand but my wife is ill with dengue fever. Can I renew on her behalf?

ANSWER: If you are sick or receiving treatment at a hospital, you can send someone on your behalf to renew extension of stay. But, you will need to get a doctor’s certificate to show the Immigration officer. Please note, if you overstay you will still need to pay the 500 Baht per day fine even if you have a doctor’s certificate.

No medical issue is a valid reason for overstay. There are wellknown cases that patients during where in hospital when the visa expired and had to pay overstay fee. And risk a negative notation. So yes. Normal overstay rules apply. You need to let some one file for your extension. The hospital can do that to or write at least letter about your medical situation. Thats the procedure

Once OA then always OA. Meaning your extension has certain demands which are different from a similar Non O (retirement). With a OA you always have to proof your in and outpatient health insurance.

One advise. Get yourself informed about Non O versus Non OA. In the end you can do the same but a Non O is more easy. No demand for insurance, no healt check or criminal check prior to getting the visa.