Depending on where you are with your career and education trajectory, you could look into something like the Peace Corps. If that's not a commitment you are ready to make, then do a search for international organizations that focus on the area you are interested in volunteering for; for example, Doctors without Borders or the Red Cross. Then you can reach out to them and see if they have any student-based volunteering opportunities. If you belong to a religious organization, there are often "mission trips" or other opportunities to volunteer outside of your country. You could also reach out to your career counselor or the study abroad office and see if they can point you in the right direction.