The Korean equivalents of “thank you” are 감사합니다 and 고맙습니다.
감사합니다 > 감사해요
고맙습니다 > 고마워요 > 고마워
You can say it in various ways, but you can see that the more informal you want to be, the shorter the speech, and the more respectful you want to be, the longer the speech.