If I were you, I wouldn't feed him the pea. Bettas are carnivores, it just seems unhealthy to me to feed them greens... There are a bunch of other ways to prevent bloat than feeding peas...
1. Fasting- Just fasting once a week with no food at all is a good way to prevent bloat.
2. Soaking pellets- soaking pellets in tank water till soft will prevent the food from swelling in the stomach, helping prevent bloat.
3. Cutting back food- A betta's stomach is only as big as it's eyeball. Simply cutting a couple pellets out of their diet a day will prevent bloat.
4. Feeding fibrous meaty foods- Instead of a pea, feed brine shrimp or daphnia to your betta once a week instead. They are fiber packed, and made out of meat, not greens! :)