A steady flow of money for the Sydney sprinter Sea Siren has forced bookmakers to continue to trim her price ahead of Sunday week's Hong Kong International Sprint (1200m).

Sea Siren opened at $3.80 with Centrebet which has been hit with a series of big bets since business opened on the international meeting on Monday, forcing her into $3.50.

The John O'Shea-trained mare heads the betting in front of locals Lucky Nine and Time After Time who finished first and second in the sprint trial at Sha Tin last Sunday week.

Australia's other entrant at the meeting, Alcopop, is listed at $12 in Hong Kong's richest race, the Hong Kong Cup (2000m).

Favourite for the Cup is the world's highest-rated racehorse, Cirrus Des Aigles, at $2.70, ahead of last year's winner California Memory at $6.50.

The 2010 Melbourne Cup winner Dunaden holds the top line of betting in the Hong Kong Vase (2400m), a race he won last year, at $3.80, although, like Sea Siren, he is certain to be at far more generous odds on the Hong Kong tote on the day.

Second pick at $4.40 is English stayer Sea Moon with last year's third and recent Japan Cup failure Red Cadeaux at $8.

Hong Kong's horse of the year Ambitious Dragon is the $4.40 favourite for the International Mile (1600m) at $4.40 from another local Glorious Days.