Heat oil in a large pan or wok over medium heat.
Add ginger garlic paste and sauté for about 30 seconds until fragrant.
Stir in the Thai red curry paste and cook for 1–2 minutes to release its aroma and deepen the flavor.
Pour in the coconut milk and stir well to combine with the curry paste.
Let it simmer gently for 3–4 minutes so the flavors blend.
Add the sliced chicken to the simmering curry.
Cook for 5–7 minutes until the chicken is fully cooked and tender.
Add the red and yellow bell peppers and green beans.
Cook for 3–4 minutes until the vegetables are tender but still slightly crisp.
Stir in lime juice, brown sugar, oyster sauce, soy sauce, and fish sauce (if using).
Add chilli flakes to your preferred spice level.
Taste and adjust sweetness, saltiness, or acidity as needed.
Pour in the cornstarch slurry while stirring.
Simmer for 1–2 minutes until the sauce thickens slightly and becomes glossy.
Turn off the heat and stir in Thai basil.
Garnish with fresh cilantro.
Serve immediately over steamed jasmine rice.