VOA for a Canadian in Beijing

As a Canadian Citizen, can I obtain a VOA in Beijing after departing from Bangkok? I need to do a border bounce on my Thai visa and would like to see the Great Wall with my Thai girlfriend (who has a Chinese tourist L). I don't think I'll have time to get it before leaving BKK as I must exit on or before the 4th of August.

Will I have a tough time with the airline if I don't have one prior to departing?
Thank you!