think vs thing coming

[mlc]

Everyone I know says, " If you think ..., then you've got another THING coming" to indicate that there is no hope of something happening. In a novel I was reading, the character said " ... then you've got another THINK coming." I googled it and there seems to be no agreement as to which expression is the original / correct version. Which version do you use? Anyone have any authorative information as to which way it's supposed to go?

[Tdol]

I say 'you've got another think coming' too.

[Nikole]

Both variants are pretty acceptable. You may say either thing or think.