** MGM China's 2282.HK stock falls as much as 4.2% to HK$11.19
** Stock on course for the biggest one-day pct drop since March 20 and leading slide in Macau gaming stocks
** Macau posts a 5.5% rise in April gambling revenue, slowing from a 15% jump in March gambling revenue
** Rivals SJM 0880.HK, Wynn Mcau 1128.HK, Sands china 1928.HK, Galaxy Entertainment 0027.HK, and Melco International 0200.HK down between 0.5% and 3.8%
** YTD, MGM China down 14.2%, SJM down 14.9%, Wynn Macau down 5.9%, Sands china down 18.4%, Galaxy Entertainment down 15.9%, and Melco International down 5.8%, while Hang Seng Index .HSI up 1.4%
(Reporting by Donny Kwok)
((donny.kwok@thomsonreuters.com))