Regulations like this were in all the hotel rooms we saw in Vietnam. I liked
checking out the standard of their English. This one scores 100% for spelling
("laundrying" just makes it into the O.E.D.), 90% for grammar (minor mishaps
with the passive voice). But forget the English usage — look at Regulation 3!
(In practice, that regulation is not enforced – not with Australians, anyway.
The rule in some hotels was expressed as a prohibition against prostitution.)
Incidentally, this was the best accommodation we had during our Vietnam tour.
There are two Vinh Hung Hotels in Hoi An. Heard well of the other one, too. A+++