Writing Feedback / Introduction of essay: How to become a doctor [3]

Please help me to check my grammar, hook, background information, and thesis statement in this introduction.

Being a doctor is not easy. Most people want to be a doctor, but the competitive examination for being a Medical student in Thailand has high competition rate. One-third of students who want to be a doctor can passing an exam and they can be a Medical student. Accordingly, students should prepare themselves while they study in Grade 10. Moreover, passing an exam is just the first step to become a doctor. Medical students have to study for six years. We can divide to be four levels, Freshmen, Pre-clinic, Clinic, and Extern and each levels and each levels has to study many subjects.