One earlier thread referenced a newspaper article which said the OED quoted 'another thing coming' from 'Only Fools and Horses', series one episode six. I found the programme, and David Jason definitely says 'another think'. Though blocked at the time, I have since accessed the OED quote. It is in the definition of 'khazi' (also in the same sentence). It seems the subsequently published scripts, whatever form they are in, may well say 'thing'. However - original script or not - Jason gets it right. He uses a definite glottal stop to indicate the 'k'.