You can probably go with one of these.
- 그래요? - You think so? / Is that right?
- 하하, 그런지도요 - Lol, maybe I am.
- 글쎼, 그럴지도 모르죠 - Well, maybe so / Maybe you are right.
- 그렇게 생각하세요? - You think so?, in a long form.
If you want to be playful,
- 물론이죠 - Of course (I am).
- 당연하죠 - Of course / No need to even say it.
- 이제 아셨어요? - Did you just find that out?