One of the most common questions we get is how do I put my Thai wife on my tax return. The first thing you have to do is to apply for an ITIN number for her. However you may not have to.
A nonresident alien may file a joint return if (s)he is married to a U.S. citizen or resident at the end of the year. If the couple files a joint return, both spouses are treated as U.S. residents for the entire tax year. If a taxpayer chooses to be treated as a U.S. resident, both spouses are taxed on worldwide income.
However a taxpayer is considered unmarried for head of household purposes if the taxpayer’s spouse was a nonresident alien at any time during the year and the taxpayer does not choose to treat his or her nonresident spouse as a resident alien. A taxpayer’s spouse is not a qualifying person for head of household purposes. A taxpayer must have another qualifying person and meet the other tests to be eligible to file as a head of household.
In short if you have a child you don’t need to include your non resident alien wife on your return. However if your wife does not have any income it may lower your taxes if you have any because the standard deduction is increased.