According to the QS World University Rankings Chula is the highest at 252  place . ( https://www.topuniversities.com/university-rankings/world-university-rankings/2016 ). 1 place higher than last year but Mahidol has shown the most improvement from 295 to 283 in the world !

I wouldn't put too much store by these rankings - it is inevitable that criteria have to be to a greater or lesser extent subjective and in this case science and occidento-centric.

i think a meta-study of all the ranking bodies around the world might reveal certain trends, but to consider one as the be-all and end-all would be misleading.