Is the 60-day visa extension for visiting family limited to once per year or once in a lifetime?

Definitely once per entry.

I have used it many times

Once per entry, although some immigration offices only issue one extention per visa.

Okay, sorry didn't even bother to read the responses

The way a 60 day visit thai family extension (which you can get based on marriage OR based on raising half thai kids) REALLY is

IS like this

Some immigration offices allow you to get the 60 day extension once PER ENTRY <- meaning you could get it off every 90 day entry from a Non-O visa if you wanted to

BUT

Some immgiration offices allow you to get the 60 day extension once PER VISA. <- meaning you can get it ONCE on a year-long, Non-O visa and then you couldn't get it again until you went and bought a new visa.

The offices that do it once a visa also look at it as once per extension. SO if you have been getting yearly extensions one after another for many years AND at any time you already got that 60 day visit family extension they won't let you do it again. AND those offices will look in the computer to see if you got it on a previous passport too. They are persnickety about it

I think the OP refers to a 60 day EXTENSION OF STAY based on family.

Which can be done once per entry (of course u aint gonna do an extension of the extension)

And (some) offices only allow 1 per visa validity (for the 1 year Non-O that would mean do it once in whichever entry u like)

In normal times (AKA: NOT NOW) it would make sense to come into the country on day 364... get 90 days... and do the 60-day extension on that last entry... thats how historically people got 17 months outta that visa.

Nonsense I've never heard this before?

what country are you from?