At the moment, TOPS supermarket is selling 250g jars of Marmite for 199 baht, which is a massive reduction over their normal price, which makes it cheaper to hire a private jet and import it from the south of England yourself.
I love Marmite, and it's been ages since I ran out, so this is a pretty good deal, while it lasts. And no, it's not past its sell-by date.