I got this paragraph from website "The Hague University". Hope it helps.
Foreign students from non-EU member states must obtain a work permit if they want to work in addition to their studies in the Netherlands. A work permit can be provided by the employer. Non-EU students need a residence permit and registration at the Town Hall. Depending on the country of origin, a tuberculosis check might be needed. These documents are necessary to obtain a social-security number (sofi-nummer) at the Tax office. Non-EU students are allowed to work for a maximum of ten hours a week.
When you are working in the Netherlands are obliged to take part in the Basic Health Insurance. More information.