In a heavy-bottomed pot, add the oil and the curry paste and saute over medium heat for about 2 minutes.
Add the chicken and toss with the curry paste, then add the stock and simmer gently for 15 minutes or until the chicken is fork tender.
Once the chicken is done, add the sugar and 1 tablespoon of the fish sauce and stir to mix. Add the eggplant, long beans, baby corn, young peppercorns, and makrut lime leaves and simmer for a few more minutes until the vegetables are done to your liking.
Turn off the heat and stir in the holy basil and spur chilies or bell pepper, using just the residual heat to gently cook and wilt them. Taste and adjust seasoning with more fish sauce as needed.
Serve with jasmine rice, enjoy!