He's just a sentimental lad, honoring the memory of his late uncle King Edward VIII.
Most Thais are too skinny to pull that one off.
Part of Halloween is about mocking the things we fear. Murderers, cannibals, and things that most of us don't even believe in. Spite the devil.
My scariest Halloween incident was when living in a US suburb, shovelling out candy to the kids who rang the doorbell. At one point I opened the door and there were two girls, about ten years old. One of them was wearing some very shear, non-opaque cloth. All I could think of was "get this nearly naked kid away from my house!" I was so shaken I dropped the candy bucket. After they were gone and I calmed down I realized that was her self-made costume of the princess from the cartoon-movie Aladdin, very popular at the time. The girl was olive-skinned, so I guessed she was seeking a character who she resembled. Very creative.