Toast the whole spices in a dry skillet over medium heat until fragrant—White peppercorns, Coriander seeds and Cumin seeds—then crush or grind them finely and set aside.
Prepare the fresh aromatics: trim and thinly slice the pale part of Lemongrass, peel and slice Galangal, clean and roughly chop Coriander roots, peel Garlic cloves and Small shallots, and zest the Makrut (kaffir) lime zest.
Make the green curry paste by pounding or pulsing in a blender the toasted spice mix with the chopped aromatics and chiles: Green Thai bird's eye chilies, Green spur chilies, the prepared lemongrass, galangal, coriander roots, Makrut (kaffir) lime zest, Garlic cloves, Small shallots, a spoonful of Shrimp paste (kapi), a pinch of Coarse salt and the crushed toasted spices—add a little of the thick part of the Coconut milk to help form a smooth paste if needed.
Slice the Boneless skinless chicken thighs into bite-sized pieces and halve or quarter the Small Thai eggplants; rinse the Pea eggplants and drain the Bamboo shoots if using canned.
Heat about 1 cup (or the thick top layer) of Coconut milk in a wide pot over medium heat until the oil begins to separate, then add the prepared green curry paste and fry, stirring, for 2–3 minutes until aromatic.
Add the sliced Boneless skinless chicken thighs to the pot and stir to coat in the paste; cook a few minutes until the edges begin to change color.
Pour in the remaining Coconut milk and about 1/2 cup Water (add more if you prefer a thinner sauce), bring to a gentle simmer, then add the Small Thai eggplants, Pea eggplants and Bamboo shoots. Simmer 8–12 minutes until the chicken is cooked through and the vegetables are tender.
Season the curry to taste with Fish sauce and Palm sugar, stirring until the sugar dissolves—adjust salty, sweet and spicy balance as desired. Tuck in torn Makrut (kaffir) lime leaves and simmer another minute to infuse their aroma.
Remove from heat and stir in a handful of Thai sweet basil leaves (horapha) and sliced Red spur chilies for brightness and a fresh finish.
Serve the curry hot with steamed Jasmine rice to soak up the rich, fragrant sauce.
