No, it's not correct. สิ่งที่คุณจะเห็น means The thing/things you will see...(which is simple present tense)
But if you want to say "What you wanna see?" , you have to say อยากดู___อะไร(ค่ะ/ครับ)?
อยาก = want
ดู = see, watch
อะไร = what
ค่ะ/ครับ = each sentence need to be followed by ค่ะ(for female)/ครับ(for male) to make it more formal or be polite. If you speak to your friends, you can omit it.
The blank space between อยากดู and อะไร(ค่ะ/ครับ) is for you to put the nouns in it. But it's still be okay if you just say อยากดูอะไร(ค่ะ/ครับ), and we still understand.
Ex. for อยากดู___อะไร(ค่ะ/ครับ);
อยากดูหนังอะไร(ค่ะ/ครับ)? = What movie do you want to watch?
Ex. for อยากดูอะไร(ค่ะ/ครับ);
when you are at somewhere like movie theater or department store, you can just say อยากดูอะไร(ค่ะ/ครับ)? which means what movie you wanna see? or what do you want to shop or go to see first?