I'm a canadian in Thailand, can I apply for china tourist visa in Bankok?

If you are not residing in BangKok, I'm afraid you can't get the China visa there.

That's not necessarily true. However, it would be prudent for your friend to send you an invitation letter in order to apply for it there. It is easier to apply for and receive one if you have an invitation letter, even compared to applicants who can furnish air tickets and hotel bookings.

You can always apply in Chiang Mai otherwise as they seem to be more lenient. Or perhaps try Vientiane, Laos which has a similar reputation to Chiang Mai. Both cities are about equidistant from Bangkok, with Vientiane being slightly closer but of course it's in another country.