Sure. If the tank is large enough to support the platies (atleast 10 gallons) they should be fine. Keep in mind though, that some bettas will attack fish with bright colors. If you have an agressive betta, he may nip at the platies. Likely not though.
Live in the Western MD/West Virginia/DC Metro Area?
Join our very active regional forum Here
Like the advice someone just gave you? Add to their reputation! Click on the balance icon underneath their username and let them know.