To become a voluntary member of the Social Security System (SSS) in the Philippines, you need to apply through the SSS website or any SSS branch. As a voluntary member, you can continue to make contributions even after leaving your job, which helps maintain your benefits like pensions and loans. It's important to ensure that your contributions are paid regularly to keep your membership active. For detailed guidance, visit the official SSS website or contact their customer service for the most accurate information based on your situation.