You've Got Another Thing Coming

While ripping the Judas Priest song 'You've got another thing coming' from a CD that i legally own, i realised that either i have been singing the wrong words all these years or Judas Priest have made an almighty mistake.
I always thought the saying was 'You've got another THINK coming' as in if you think that, then you've got another think coming, not 'another THING coming' which just doesn't make any sense.
As Judas Priest are from Birmingham, maybe its a regional dialect thing but the lyrics are:

If you think I'll sit around as the world goes by
You're thinkin' like a fool cause it's a case of do or die
Out there is a fortune waitin' to be had
You think I'll let it go you're mad
You've got another thing comin'
 
which means they used the word think all the way through the chorus and then changed it to 'thing' in the last line.
To further add to my theory that the singer misread the last line when he recorded it, if it is 'thing', then what is the other 'thing' that is coming?
Therefore, i propose to ignore Judas Priest and continue singing 'another THINK coming' and dismiss the official title as a legend of scruffy handwriting by the original songwriter and the lead singer being too drunk or possibly high to notice it doesn't make a lick of sense when he came to record it.