BigBill said: I wish you had included images of the whole Plumeria. That looks rotted to me.
If the top is green with leaves, you can save it my making a cutting.
Cut into green, clean healthy tissue. Then let it form a callus on the bottom and then pot it up.
BigBill said: Certainly, If the base feels soft where those holes or open areas are, cut the main stem above the green plastic tie. Make sure to look at the good end and see if the tissue is nice and white and it looks good. If it does, trim back 2/3 to 3/4 of the leaves, all except the newest few. Since you have cut it off from the root system, the plant can not support those leaves. You will lose them anyway. You can treat that new cut by sprinkling cinnamon on it, it is an anti fungal remedy.
Let it sit for 7-10 days and let a "callus" from. That is like a scab on a human, a dry end. Then you can plant it in soil within a pot. Make sure pot has drainage holes. Water it every other day. But don't soak it, water it. That will help to encourage new roots.
When it starts to produce new leaves you could re-plant it outside. if you want to. In order to bloom, it needs good direct sunlight. If it is too shaded it may not flower. Fertilize with a plant food at half strength every two weeks or so.