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If you are referring to the vine/stem, as long as the stem is firm and alive keep it. If you are referring to the leaf petiole -- the "stem" which connects the leaf to the stem/vine then you could remove it but I'd wait until it dries up and easily detaches.

This plant climbs, it's too heavy to trail. One needs to give it some support, a trellis of some kind. I happen to grow mine Hydro (in water, not soil).

These stems thicken in time & this plant leaks white sap looking like Elmer's glue. Normal, but can be messy. Another reason to consider what type of support as it's harder to bend as it gets older (& it can leak while bending).

Will show another kind of Hoya next so you can see the support I made is from a wire hanger.

Paul is right that as long as the bare stem looks healthy, it's fine. One doesn't generally cut back Hoya vines/stems even when bare, unless deliberately trying to prune / shape.

Your plant looks good from here. You may wish to secure it w/ a couple of large rocks at its base until you decide what support to give it.