grammar - Which is correct (if any): "please let me know what do you think"? or "please let me know what you think"?

I find myself unsure which of the following is more correct:

please let me know what do you think

Or

please let me know what you think

My gut feeling tells me that it's the latter...

Or are both incorrect and there is a better way to say the same thing?

Answer

Please let me know what you think

is correct. Even if do were to be included, the correct form would be

Please let me know what you do think

but this should only be used for emphasis (for example, to contrast with don't think).