Pat the chicken thighs dry and season generously with salt, pepper, cumin, and chili powder.
Heat the olive oil in a large skillet over medium-high heat.
Place the chicken in the skillet and sear for 5 to 7 minutes per side until golden brown and cooked through.
While the chicken is cooking, combine the black beans, corn, diced red onion, lime juice, and chopped cilantro in a small bowl to make the salsa.
Remove the chicken from the pan, let it rest for a few minutes, then slice into thin strips.
Warm the corn tortillas in a dry skillet or directly over a low gas flame until soft and pliable.
Build the tacos by layering the sliced chicken, black bean salsa, and fresh avocado slices into the tortillas.
Finish each taco with a dollop of Greek yogurt for a cool, creamy finish.