Surrendering green card and paying student loans

I have 4,000 dollars of debt from when I went to university. I have been paying off my debts in time. US law requires that I surrender my green card if I will be out of the country for more than six months. Due to family matters I might have to move abroad for a few years. I want to keep paying my student loans even though I would have to give up my permanent resident status. I read online that supposedly I have to pay in one go everything before I surrender my green card. Is this true? I understand that non residents do not benefit from financial aid, so that kind of makes sense [although it still sounds crazy]. Or can I keep paying every month regardless of being a resident or not. I want to pay all my debts because I do not want to get in trouble and would like to visit family in the US in the future.