What Legal Action Do Online Payday Loans Take To Get Their Money Back?

It depends on the state you are living in and on the type of loan you took out originally. There may be some information in the contract you signed or agreed to when you took out the loan so check the fine print details first.
In short, most online payday loan companies will keep adding on interest charges until they have received the loan payments back in full. As long as they can see some evidence of the borrower making some repayments every month, there will be no need for them to take legal action against them.
In the event that the loan has not been paid back, some lenders in certain US states can take legal action against borrowers. Although, there are some states where it is actually considered to be illegal for a lender to give a payday loan to a borrower, so if they refuse or are unable to make the repayments- it is unlikely there will be any repercussions. Some of the states were lenders do not have the legal standing to offer payday loans include Kansas and Kentucky. 
The best thing to do before taking out a payday loan is to check your finances and make sure you will be able to make the monthly repayments. Also make sure this type of loan is actually legal in your state, because if you do know you are committing an illegal act you could actually risk prosecution for accepting a loan of this type. Check your state laws before signing any payday loan agreement.
When a lender does have the authorization to offer the loans, they will probably pass the debt on to a debt collecting agency. This will mean the borrower may not only put their chances of securing credit in future in jeopardy but also their property.

Most online payday lenders don't have much of a leg to stand on. In the state of Ky. For instance, you cannot be prosecuted if you do not repay an online payday loan...or even a store front loan. Criminal prosecution in Ky., Kansas...and in several other states is illegal.  You have to research your particular states laws. Personally, I feel that payday loans are immoral and should be illegal. When I say immoral, I mean on the part of the lenders. They charge outrageous fees, and they know that most people cannot afford the repayments. How in the world anyone ever thought up the idea to establish these criminal enterprises is beyond me! They are just as bad as going to some loan shark on the street to borrow money. If they call you and threaten you with jail etc...don't believe it. The most they may be able to do, is sue you for the balance that you owe, but if it is an internet pdl place it's highly unlikely that this will occur, because like it was stated previously, most internet pdl places do not have a license to lend in several states. Some do however, but still they would not be able to file criminal charges for non payment. Most of the time these cases will usually wind up going to a collection agency.  Again however, these places should be outlawed because they are guilty of predatory lending. They are no better than the banks that for yrs. Were giving consumers sub-prime loans. Consumers need to write letters to their Congress people and Senators, and let them know that something has got to be done about payday lenders, and that the industry should either be outlawed, or regulated, and slapped with huge fines, and lawsuits for harassing customers that default and for charging outrageous fee. As far as I can see, these people do not provide a humane service for people. They exploit people and squeeze them dry.

Also  in the state of ky internet payday loans are illegal