International students in Singapore?

Most residents of Singapore are known to be foreigners, therefore this contributes to Singapore's large communities of people of different ethnicity and race. So, consequently, it shouldn't be difficult for foreigners to not only get a student visa, but also be allowed for part-time jobs and internships. However, after contacting several universities, I realized that Singapore normally allows foreigner students to neither take up part-time job nor internships. How come that is possible? Is it really true? If yes, could you please provide me with the information regarding my concern from the official sources. Thank you for your attention.