Do I need a visa to buy a transit ticket for Hong Kong tourists? Can I go for a day just by buying a ticket? Do you need any other formalities?

Let me explain to you what a transit tourist ticket is:

A "tourist transit tourist ticket" can be used by all tourists within one month from the date of invoice, within one day after the first use or within two consecutive days [2]:

Take the Hong Kong Island Line, Tsuen Wan Line, Kwun Tong Line, Tseung Kwan O Line, Tung Chung Line, Disney Line, east rail line Ordinary Line, etc. [3], Ma On Shan Line, and so on indefinitely. And

take or return to lo wu station or Lok Ma Chau Station and the Island Line, Tsuen Wan Line, Kwun Tong Line, Tseung Kwan O Line, Tung Chung Line, Disney Line, east rail line Ordinary Line, Ma On Shan Line and west rail line twice by car.

The above two tickets are only available for less than 14 days in Hong Kong and can be presented! ! Valid travel certificate! ! Passengers.

so it's just a package ticket for taking the subway. Therefore, you still need to apply for the "Pass to and from Hong Kong and Macao" and apply for a Hong Kong endorsement.