Yes, Chúa means God, it also means Lord. Trời means Sky, also God. We usually use "Trời" for Sky tho, and when we use it for God, we add-in the word "ông" (Grandpa/He) to make it clearer if there is no context. "ông Trời" = "God" or literally Sky Grandpa! Mặt Trời = "Sun" or literally Sky Face! "Trời ơi!" = OMG!