I apologise for answering you in English but it is much quicker for my slow fingers to concentrate on 26 alphabets instead of 44. Anyway, I'll try to avoid using technical terms.
I think that the root difference that has led to consequent differences is the system.
But, we must ask, how different?
Firstly and most importantly, Thai edu tends to "force" rather than "interest" the students to study. This can be demonstrated by the fact that the students can't choose subjects they prefer and the fact that Thai students are supposed to be disciplinary and are not supposed to contradict their teachers. This system generates the inability to think creatively and decreases constructive bravery needed for revolutions. It also causes revolts toward schools and, therefore, a decrease in academic performance. And, interestingly, it imply the students and parents that there is only one dimension of success, academic achievements. This results in discriminations between those with academical and non academical talents and an increase in the competitiveness of Thai education and this is when additional tuitions begin.
Secondly, Thai edu uses multiple choice exams to measure the students' achievements due to the large number of students contributing to the inadequate budget whereas in western country ( or at least in NZ where I am studying), subjective examinations are the main tool for evaluating the students' achievements. This use of multiple choice exams results in, again, lack of creative thinking and the ability to express information.
Lastly, instead of using levels of understanding as a sign of achievement, Thai education, somehow, give more weight to the "effort" that leads to "grades". This does not indicate the actual potential of success. Being unable to rely on the grades, universities are forced to invent another test for admissions. Since working hard in class does not increase the chance of entering to Uni, the students have to rely on the more efficient way, additional tuitions.
And these are the causes of Thai education problems.