Hi Luis, sorry, couldn't seem to add a picture to my original question. Here's a photo from my garden. Thank you, Sim.

compare here: https://duckduckgo.com/?q=Plumeria+%22Frangipani%22+seed+pods&t=ffcm&iax=images&ia=images

have you tried opening one??

ken

Don't open one ;0)

It takes seed pods 9 to 10 months to ripen. They must remain on the
plant during this time. If they are taken off earlier, the seeds do not
mature. In some plumeria cultivars, the pods stay green right up to the
time the seeds are ripe. In other cultivars, the pods turn brown or
purple as time goes on. The color change doesn't mean they are ripe. The
pod opens down one side when it is mature. Just before splitting open,
the pod begins to shrivel and look drier on the outside.

Also -
To save the seeds, when you notice the pod beginning to dry slightly,
cut the toe end from a panty hose leg and put it around the pod,
fastening it to the stem end of the pod. You can also use a piece of
organdy, tulle, or cheesecloth

To sow

Soak dry seeds overnight. The thick end of the seed opposite the papery end -- the plant embryo --
should be starting to swell. Put the seeds in a well-drained, sterile
potting mix, embryo side down. Just barely cover.

Seeds should germinate within two weeks

Thank you so much! Thank you for all the information you have shared and the great tips! :o)

Yes, wait until they open and split down middle like in this picture to make sure the seeds are good:

https://images.search.yahoo.com/yhs/search;_ylt=AwrEeBzyKo1foGwAMAQnnIlQ;_ylu=Y29sbwNiZjEEcG9zAzEEdnRpZAMEc2VjA3Nj?p=open+plumeria+pods&fr=yhs-mozilla-102&hspart=mozilla&hsimp=yhs-102#id=0&iurl=https%3A%2F%2Fplumeria.today%2Fwp-content%2Fuploads%2F2018%2F01%2FSeed-Pod_7727-300x200.jpg&action=click

If the pods prematurely falls then discard it.