Billytea, are you telling me tat my interpretation is unconvincing, or wrong, or what?

Unconvincing, I suppose. I've never come across the expression before, so maybe it's used in an idiomatic fashion; but the meaning you presented doesn't seem to be in line with the words used.

Your acceptance won't make it any more true, just like your rejection doesn't make it any more false.

True. My line of reasoning, however, may indicate whether it was true or false, independent of what you or I thought it meant.

To further the issue, Vortex stated that the earliest usage was:

"Conroy lives in Troy and thinks he is a coming fighter. This gentleman has another think coming. It is probable that McCoy will next meet Joe Choynski."

My reading of this statement is that it wasn't even addressed to Conroy. I don't see how it can be read as saying "Think again"; I do see how it can mean "You're about to find out how wrong you are" (or more precisely, "[Conroy] is about to find out how wrong [he] is". When he fights Choynski, I take it.)

And the "thing" expression is an eggcorn, and it doesn't matter how long the posts in defense of "thing" get--still eggcorn, and "think" still original and meaning what I said.

I have numbered... stuff!

1. What's an eggcorn?
2. In this thread, near as I can tell, your use of the phrase was simply to seek confirmation that other people used "think" rather than "thing". Is there a use elsewhere that provides context to "meaning what I said"?
3. As you'll recall, my position on the matter is that "you've got another thing coming" makes perfect sense in any case. I am not saying there is a single phrase, and it has to be either "think" or "thing". I'm saying that regardless of whether people somewhere use "you've got another think coming", "you've got another thing coming" is a grammatically correct and usable phrase in its own right. And since it doesn't have to start with "You think that...", and I don't recall ever hearing it in that context, I don't see them as being in exact equivalence. (IOW, FLYING SQUIRREL SUPREMACIST!)
4. Lists are fun!

I can't really speak to the error/retcon stuff, as I regard it as neither. (Even if there had to be One True Phrase, given even "thing" has been around for almost a century, I feel the statute of limitations has passed on demanding modern communication find the original more congenial.)

I've never heard of an eggcorn before, either, and my head keeps trying to make it an egg cream.

I must say, I rather like Think as a noun and will work it into casual conversation ASAP.

Ooh, egg cream. I have the ingredients for one of those! Hello, breakfast.

Eggcorn is a fake/wrong etymology (?) for acorn, so became what they call it when people talk themselves into a reasonable-sounding but wrong explanation for a word.

Eggcorn is a fake/wrong etymology (?) for acorn, so became what they call it when people talk themselves into a reasonable-sounding but wrong explanation for a word.

Oh, ok! Like imagining Hendrix to be singing "Excuse me while I kiss this guy." (My favourite misheard song lyric is "There ain't no girl like the One-Eyed Gott.")

Apparently the NZ eventing team got arrested for drinking in a non-drinking area.

Wait, what part of London is a non-drinking area? I didn't realize that existed.

I am wearing a new dress today (this one [link] from the Land's End sale). happy making.

Am interviewing a potential new caregiver tonight. The house is a bit of a mess, but I did a quick clean-up of 2 areas this morning. I am hoping I can get home early enough to clean the litter out and do a quick mop of the entry way.

Oh, ok! Like imagining Hendrix to be singing "Excuse me while I kiss this guy."

That's a mondegreen.

Like imagining Hendrix to be singing "Excuse me while I kiss this guy."

This one is a poor example, as my mother swears that Hendrix used to deliberately sing it that way at live shows and point to "this guy" in the audience to make it clear.

(Besides, "The ants are my friends / they're blowing in the wind" is much funnier.)