Marmite or vegemite, call it what you will, and as they say back home, love it or hate it, but I want some.

I just need to know where sells it

Nong Khai Direct, right next door to our office on Chaloemphrakiat Road sells it, and has plenty in stock, I just checked for you.

Just head for the bridge and make a U turn right before you drive into the checkpoint area and then take your 1st left into the car park and it's straight in front of you. They carry a large selection of other farang foods as well.