Ronda Rousey: Nearly Nude and in Knockout Shape for S.I. Spread

Ronda Rousey's confidence is back to champion form, and TMZ Sports has the hard evidence -- Ronda sporting NOTHING but body paint on a Caribbean beach!

The ex-UFC champ is doing a photo shoot for S.I.'s upcoming Swimsuit Issue on Petite Martinique island, off the coast of Grenada. We checked, and what looks like a swimsuit ... is just paint.

As you can imagine, Ronda's shoot on a public beach drew plenty of attention ... hence these pics.