In a large bowl, combine garlic, shallot, ginger, turmeric, coriander, cumin, chili powder (if using), soy sauce, tamarind paste, salt, and sugar. Mix well.
Add the chicken pieces and coat them thoroughly with the marinade. Cover and refrigerate for at least 1 hour, or overnight for more flavor.
Heat the vegetable oil in a large skillet or frying pan over medium heat.
Add the marinated chicken pieces and cook, turning occasionally, until they are golden brown and cooked through (about 20-30 minutes). Adjust the heat as needed to avoid burning.
Reduce the heat to low and pour the coconut milk over the chicken.
Simmer for an additional 10-15 minutes, allowing the coconut milk to reduce slightly and the chicken to absorb the flavors.
Remove the chicken from the skillet and place it on a serving platter.
Garnish with fresh cilantro or basil, if desired.
Enjoy your meal!