Paul never refers to Jesus returning; only coming, as in a first time.
Isn't a return implied by what he says in 1 Cor. 15:20-44?
But Christ has indeed been raised from the dead, the firstfruits of those who have fallen asleep. For since death came through a man, the resurrection of the dead comes also through a man ... But each in turn: Christ, the firstfruits; then, when he comes, those who belong to him ... But someone will ask, “How are the dead raised? With what kind of body will they come?” How foolish! What you sow does not come to life unless it dies ... So will it be with the resurrection of the dead. The body that is sown is perishable ... it is sown a natural body, it is raised a spiritual body.
I think what Paul means by "when he comes" is when Jesus comes in his spiritual body, the one that was raised after his "natural body" was sown. This is because, as he says in 15:50-51, "flesh and blood cannot inherit the kingdom of God," and for this reason even the living will have to "be changed, in a flash, in the twinkling of an eye, at the last trumpet."