Depends on the species.
Betta splendens, yes, one male, or a group of females provided it is heavily planted and monitored for aggression. A pair might work as well, but you'd want to monitor the female to be sure she isn't harassed.
But there are lots of species of bettas, many which are fine in community or species only setups. Betta ocellata, patoti, coccina, rubra--all are mouth brooders and will be fine in a colony setup. The exact count depends on the species, since ocellata are 4-5 inch fish and patoti are 6-7 while coccina and rubra max out at about 2 inches.I have a planted 37 with ocellata and there are about 20 fish, ranging from adults to fry.