Proof of transit

Hi,

I'm interested in booking two round-trip flights Canada to Shanghai for 10 days, and within that timeframe travel from Shanghai to Hong Kong for lets say four days out of the ten. Would that work for the 144-hour TWOV rule? Technically it's three countries, but wouldn't appear on the same ticket. I would plan to show my second booked flight as proof that I'd be leaving Shanghai. My flight back would thus be from Shanghai to Canada in the end.