Plumerias do get top-heavy in pots. You can partially bury the pot in soil, and additionally pound a piece of rebar down through the soil and into the ground. If you have it on a deck, you can tie it to the railing with bungee cords. If you have it in the open on a tile or cement patio, you can stick it in a larger heavy ceramic pot. Lots of options. But we don't know where your plant is.

I live on the Mississippi Gulf Coast. The two plants are on my front porch. The pots are light weight. Right now we are getting a lot of rain.