Heat a large pot over medium heat and add the curry paste.
Cook for about 1 minute until fragrant.
Add the coconut milk and stir to combine.
Pour in the chicken or vegetable broth and bring to a simmer.
Add the chicken, tofu, or shrimp, and cook for about 10 minutes.
Stir in the sliced bell peppers and green beans.
Add fish sauce and sugar, adjusting to taste.
Simmer for another 5-10 minutes until vegetables are tender.
Remove from heat and garnish with fresh basil leaves.