** HK shares of China's thermal and coking coal producer Yankuang Energy Group 1171.HK fall 4.2% to HK$9.32; set for biggest one-day pct decline since June 5

** Stock top pct loser on Hang Seng Composite Index tracking energy stocks .HSCIE, which is down 0.2%

** Shanghai-listed stock 600188.SS loses 1.2% to 13.12 yuan, lowest since August 6

** Yankuang Energy sees H1 net profit plunging 38% y/y amid significant decline in coal prices, surplus balance of coal supply and demand in general

** YTD, HK stock gains 4.6%, Shanghai shares fall 6.9%

(Reporting by Donny Kwok)

((donny.kwok@thomsonreuters.com))