USA to HK flight, train to Guangzhou, flight to Thailand?

I want to visit my cousin in Guangzhou before my trip to Thailand. Starting in the USA Delta airlines will fly me in to Hong Kong via a stopover in Tokyo. I could then take a train (or perhaps fly if required) to Guangzhou. Then take a regional carrier to Thailand from either Guangzhou or Hong Kong if there any feasible options to use the 72 hr free transit. Can I make it work? Thanks for your help!