Both are Thai BL drama/movie that are very similar, being about a creepy old house and ghost(s) that live in that house. They are both about the supernatural with some historical and suspenseful themes.
Both are Thai BL dramas about a main character living in a house with a ghost, with him needing to solve the mystery of the house. He's Coming to Me is more light-hearted while The Hidden Moon is a bit darker.
Both are historical Thai BL dramas with a past and present timeline that features a love story between a human and a ghost that is trapped inside an old house.