Well the thai version of red bull contains Ma Huang which contains Ephedra alkaloids, in otherwords its basically a liquid Ephedrine/Caffiene stack with tonnes of sugar (so negates the fat burning effect but gives you a buzz)

That's why a) it's stronger than the british version and b) it's banned in this country

Thermos are basically a collective name for the fat burners that increase heart rate and metabolism and core body temperature. Most of the stuff banned in the UK for stupid reasons had ephedrine in them. I am not anti ephedrine at all since it's herbal and very safe if taken properly! but it was touted as speed to kids who thought they were taking a drug and misused them.

Thermos now have a weaker variant of ephedrine in them called Synephrine which has very mild stimulating effects (wherelse ephedrine had a higher rate but I still think it was the caffiene as the main contriutor to the effect, ephedrine just helped supress apetite more thus it became a fat burner but studies did show it helped burn actual fat)