Yes, platies can be kept with bettas. Because platies are peaceful and non-violent, they make great tank mates for many other species, including bettas. Platies won’t get in the way of the bettas or provoke any aggression.
With that said, there are several things you should consider when keeping platies with bettas. First, you should keep at least three platies and just one betta in the tank.
Also, because the platies are quite active, they require plenty of space to swim around. A 20-gallon tank is a minimum for this species combination.
Don’t forget to add plenty of plants and hiding places to prevent conflicts. Lastly, monitor the tank dynamics regularly and be prepared to separate the fish if aggression occurs.