If you don't pay your payday loan back it will go to collection to a third party collector normally after 120 days. At this point they can get a judgment on you. If you fail to appear in court the judgment is automatically awarded to the creditor. At this point they can now garnish your wages, levy your bank account, or place a lien on any property you own such as a car or home.
You will be sued for not paying it. They have your personal information and they have a lot of proofs so if you don't want to cause more troubles for yourself, pay it. You can get a payday loan at http://paydayloanservices.me/ because they offer flexible paying options so you won't have to think off not paying your loan.