not badA conversational way to express mild approval. ก็ can add a sense of “actually” or “after all,” while นะ softens the statement and makes it sound friendly.
TH: ร้านนี้อาหารแพงหน่อย แต่ก็ไม่เลวนะ
EN: The food at this restaurant is a little expensive, but it's not bad.