In wide, shallow bowl or deep plate, combine 2 tablespoons of yogurt with 2 tablespoons of coconut milk, curry powder, garlic and 1/2 teaspoon salt. Mix in oil.
Cut chicken lengthwise into 12 strips. Insert skewer into bottom of one chicken strip and work it up lengthwise to top. Repeat with remaining chicken. Place skewers in curry marinade and using your fingers, make sure it coats them. Cover with plastic wrap and refrigerate for 1 to 8 hours.
Arrange marinated chicken on paper toweling and blot dry, removing all excess marinade. Heat large skillet over medium-high heat, then coat with cooking spray. Or heat stovetop griddle. Arrange skewers in one layer in pan and cook for 2 minutes, browning chicken. Using tongs, turn skewers and brown on another side, 2 minutes. Turn chicken and cook until it is opaque and hot around skewer at thickest part of chicken. Transfer skewers to serving plate.
While chicken cooks, prepare the Raita. In bowl, combine remaining yogurt and coconut milk with onions, mint, lime juice and remaining salt. When possible, make Raita 30 minutes before serving chicken to allow its flavors to develop and meld. Serve it the day it is made.