1. the percentage of money bet on each horse to win is statistically closely related to the long term winning probability. This has been proven true in many many studies and in many countries.
2. for HK, the percentage of money on each horse is
% = ( 1 - 17.5%) / Win Odds
e.g. Win odds of 2x means 41.25%. If you look at large number of historic data of all horses at 2x Win odds, they did win about 41.25%.
3. if you bet on all the 2x horse, your expected return is
2 x 41.25% = 82.5%
which means, in long term, your losses is the tax amount. Because you get back only 82.5% of your money. You need expected return of >100% to make money.
4. so to make money, you not only need to find which horse is likely to win, but more importantly which horse is paying more than its fair share as indicated by probability. Otherwise you may have lots of winning tickets but not making money.
5. race fixing is probably not a big problem in HK. Otherwise the statistics in 1 above would show the irregularity. This is probably the most scientific proof you can get.
Sorry that I cannot type in Chinese. Someone please translate for the benefit of the others.