I noticed often when the asc, mh is 0 degree, a high odd priced winner win at times.

And not at other times?

Chiron, south node conjuct axis produces high odd winners

However the mh changed sign and 0 degree some time ago and no high priced winner, why is this? Do I have check the odds?

Or can it mean small change?

In his book 'Gamblers dharma sports betting with Vedic atrology' , Simon Chokoisky says..
"Western techniques such as midpoints, Arabic parts, and antiscia, none of which have made it into our study, may well be candidates to help us make greater sense out of the messages of the sky."

When you say 'Chiron, south node conjunct axis produces high odd winners', you are at the beginning of something... observation.
And the first thing you will notice is that every time you come up with a rule, the sky has changed.
Your observation needs to have multiple factors involved not just Chiron conjunct South Node.
A stack of several observations together will lead to a more robust rule.

More important is 'What is your chart telling you?'
Once, I was at the racetrack with a friend and he said 'I will bet on the horse with the red colors'.
Racing silks and colours are used to represent a horse's owner and to allow race commentators and spectators to easily differentiate between racehorses.
And he went on to bet on the one with the green sleeves... by mistake. And he won!
If you are lucky, any system or better, no system at all will make you win.
Any system or rule (something outside) is a reflection of your inner world.

Best to you Vas!
Ouranos