Is it illegal for a hotel to open a double room with someone?

Not illegal. There is no relevant law in the country that it is illegal for a hotel to bring people in in a double room, so it is not illegal for a hotel to open a double room to bring people in. Hotels (also known as hotels, hotels, inns, guest houses, business trips, inns, hotels in China, and hotels in Malaysia and Singapore) are basically defined as business organizations that provide safe and comfortable spaces for users to have a short rest or sleep. It is a place for guests to stay and eat.