There are some places you can bet on a cockfight in Sleeping Dogs, but in this particular location in Kennedy Town you can gamble 50k in a single bet. if its the first fight you win, you will be able to win 2 trophies, Tourist Trophy / Achievement and Infowlable Trophy / Achievement.
I advise you to save your game before the fight. If you fail you are able to load and try it again.
1 Step Closer to Platinum :)
Sleeping Dogs Definitive Edition with DLCs