Iam now a US citizen, my wife reside outside US. can i file single marital status?

No, you can't file as single.  You have 3 possible options to file:

Married Filing Separate.  If you have no dependents, and your wife does not reside in the United States, you may choose to file as Married Filing Separate.  If your wife does not have a Social Security Number or an ITIN, you will have to mail in your tax return and write in "NRA" (for nonresident alien) in the Box where her Social Security Number would appear.  So that the tax return can at least print out, you will have to use a "dummy social" for her (like 999-88-9999).  You will white out that number wherever it appears and write in "NRA".

Head of Household.  If you do have dependents that qualify you to claim Head of Household, you may do so.  However, you may not claim Earned Income Credit.  There is a checkbox that identifies that your spouse is a Nonresident Alien.

Married Filing Joint.  Even if your spouse did not reside in the United States, you may make an election to have her treated as a resident for tax purposes,   This would be advantageous if she has next to no income, because Married Filing Joint is the most advantageous filing status in that circumstance.  However, she must have either a Social Security Number or an ITIN and be able to sign the tax return.  If you are able to take advantage of this filing status, file an extension to be able to get your paperwork in order.  If she does not have an ITIN, please see this Help Article on how to apply for one with the tax return:  How do I get an Individual Taxpayer Identification Number (ITIN)?