Can army officer rejoin after resignation?
Simply so, can an army officer resign?
If all service obligations have been completed, a US commissioned officer can resign, or request being transferred to a reserve status, anytime. If the officer resigns his/her commission, and something big happens (like a war), the person could be drafted, and have to return as an enlisted person.
Similarly, you may ask, can an officer go back to enlisted?
In the Army, after you fulfill your entire officer commitment, you can re-enlist as enlisted. There is no guarantee you will get it. You must still fully qualify for the enlisted position. In your scenario, assuming no age and/or physical restrictions, chances are high the Army would allow it.
In general, you cannot resign your commission until you have completed eight years as a commissioned officer. All officers need to complete the resignation letter and send to the appropriate command. If you are an IRR or IMA officer, send the resignation letter to your Career Management Officer (CMO).