Will I need an ETA for a 30 day extension in Thailand after entering with a 60-day visa exemption?

I believe you and many other people asking about this are getting the cart before the horse.. 😮

The Electronic Travel Authorization program will pilot in December <- meaning IF you enter before it starts you won't have to apply for one before you come here <- there's no indication whether you'd be asked for it or not even after the program starts to get an extension 😕

AND

As far as how it will work AFTER they roll it out it's anyone's guess.

If I were to guess, I'd say, yes, you WILL need to apply for one before you bounce out and back for a visa exempt entry AFTER the program starts in Dec.

All we can do is wait for the real announcement they will come out with telling people how it will work and when it will start. Anything right now is just educated guessing