If you need a side issue, you have to pay taxes if you are overseas. You just get to exclude some of what you make. From the IRS website
If you are a U.S. citizen or a resident alien of the United States and you live abroad, you are taxed on your worldwide income. However, you may qualify to exclude from income up to $82,400 of your foreign earnings. In addition, you can exclude or deduct certain foreign housing amounts.
If you don't file and its been more than 3 years IIRC you can't claim the exemption and have to pay taxes on all of it, plus interest etc.
