Prepare Pei Wei Asian Kitchen Spicy Peanut Sauce according to the recipe linked to in "Spotlight Recipes" below. Set aside. (This can be done in advance. Store in a tightly sealed container, in the refrigerator, until ready to use.)
Prepare Pei Wei Asian Kitchen Thai Sweet Cucumber Relish according to the recipe in the Recipe Box below. Set aside. (This can be done in advance. Store in a tightly sealed container, in the refrigerator, until ready to use up to 2 days.)
Trim excess fat from chicken thighs. Slice into 3-inch by 1-inch strips.
Thread each strip onto a bamboo skewer, weaving through the center for secure placement. Place in a shallow, sealable bowl and set aside.
Toast coriander and cumin seeds in a dry skillet over medium heat until fragrant.
Grind with a mortar and pestle or spice grinder.
In a bowl, combine ground spices, lemongrass, salt, turmeric, chili, coconut milk, brown sugar, lime juice and fish sauce to create the marinade.
Pour marinade over chicken skewers, coating well. Cover and refrigerate for at least 4 hours, or overnight for best flavor.
When ready to cook, heat a grill pan or cast-iron skillet over medium-high heat.
Grill skewers 3 - 4 minutes per side, basting with reserved marinade, until chicken is cooked through and lightly charred.
Remove from heat to a place. Set aside and keep warm.
Discard remaining marinade.
Serve skewers hot with peanut sauce for dipping and cucumber relish on the side for cooling contrast.