It is very hard to collect money internationally when people do not want to pay.
You do not have easy, direct court access nor any effective arbitration when the amount do not exceed the collection expense.
Best policies are in preventing losses. Controlling customer expenditures to reasonable levels with credit cards, whose charges can be reversed pretty much on customer demand, is a good idea. If a customer wants to spend above the limit you set have him ACH or EFT the funds in advance -- that way you cannot get burned.
Every major company I have worked for in the mainstream market established credit limits for customer purchases -- on open accounts. Credit card sales are different but they are not final cash sales -- instantly.
If you want to know how to get your money fast -- file a lawsuit and place a lis pendens on their property's title(s). Until that lawsuit is dismissed; they won't be able to do anything with their property's title like sell the property of borrow money against the property without paying a bonding company to guarantee good title -- this usually gets a debtor's attention -- either way they have to pay
Obviously, you need court access and access to the deeds office as well as a lawyer or have knowledge of how to do this.