At this time there is no such list of Men who served in the Vietnam War, were wounded (casualty) and returned to service and later an a regular discharge. The only lists available on Ancestry are Casualty Lists involving a death or being a POW who returned alive.
Fold 3 has more Vietnam Databases so you might try a short subscription period or see if your local library has one to use.
If you are trying to locate him you can send a letter through the Social Security Administeation. Instructions are on thier website. Basicly you write the letter informing him of your contact information and desire to make contact. Place it in an envelope with a stamp and your name in the return address corner and just his name in the usual place on an envelope, leave it unsealed and take to your local SSA and give it to them. They will read the letter to make sure it is not a threat or unsavory. They will then seal it and put the last address they have on file and mail it. They will not tell you the address nor can they give you a confirmation that the address is correct and it arrived. Your father may or may not respond. At least that was the procedure 18 years ago when I used the service.