Prepare the marinade for the chicken. Combine minced garlic with cilantro, lime juice, cumin, coriander, oil, salt, and pepper. Pour over the chicken, tossing to coat. Let sit for at least 1 hour or up to overnight.
Meanwhile, make the corn salsa. Heat 1 tablespoon oil in a saute pan. Add the corn kernels and saute until slightly charred, about 5 minutes. Add the snap peas and saute 1-2 more minutes or until charred. Remove from heat and season with salt and pepper. Let cool slightly and toss with tomatoes, radish, red onion, cilantro, and lime juice. Season with salt and pepper and let sit.
Heat grill to medium heat.
Cook the chicken on the grill until deep grill marks form, about 5 minutes. Flip the chicken and cook on the other side until the chicken is fully cooked, another 5-7 minutes. Remove from heat and serve with the corn salsa.