Think of the character "kou" -- "hau" in Cantonese, "k(h)au" in Teochew, resembles the Thai word khau, enter. It means a mouth and resembles a large mirror on the wall. Sometimes it can be a little more rectangular.

口

This below means "mouth of a cave":

洞口

This below means "den" in Cantonese, but if can also mean "the mouth of a hole, burrow".

竇口 dau3 hau2

Someone helps the main character: "The hotel is in that brochure that reads hau (maybe house pronounced in Thai or Cantonese way). Do not lose that brochure that has the name hau in it." And in the end hau is in every brochure.

And that character 口 is white. It is kong, empty, or kong bai, blank. Nothing can be said about it.

The answer to my problem is hidden somewhere here.

(This is of course just one of my problems.)

I don't know if even those I call trolls could give a small hint here.