From Cap371s3 of the Smoking (Public Health) Ordinance

"(3) The manager of a no smoking area or any person authorized in that behalf by any such manager may, in respect of any person who appears to be contravening subsection (2)-

(a) after indicating that the person is smoking or carrying a lighted cigarette, cigar or pipe, as the case may be, in a no smoking area in contravention of subsection (2), require the person to extinguish the lighted cigarette, cigar or pipe;
(b) where the person fails to extinguish the lighted cigarette, cigar or pipe, require him-
(i) to give his name and address and to produce proof of identity; and
(ii) to leave the no smoking area;
(c) where the person fails, as required under paragraph (b)-
(i) to give his name and address and to produce proof of identity; or
(ii) to leave the no smoking area,
remove him from the no smoking area by the use of reasonable force if necessary and detain him and call for the assistance of a police officer to assist in the enforcement of this section."

And from Cap371s7:

"(1) Any person who contravenes section 3 or 4 commits an offence and is liable on summary conviction to a fine of $5000.
(2) Any person who fails to give his name and address or to produce proof of identity when required to do so under section 3(3) or 4(2) or who then gives a false or misleading name or address commits an offence and is liable on summary conviction to a fine at level 3."