I'd just like to start off by saying, the amount of problems I've ran into while in Thailand is so sickening! Anyways, so I booked a return flight from Toronto (YYZ) to Chiang Mai (CNX), the flight here looked like this:

Toronto -> Shanghai -> Kunming -> Chiang Mai

Which was sweet and easy.

The flight back, however, looks like this:

Chiang Mai -> Kunming -> Tianjin -> Shanghai -> Toronto

Before I was able to check in at Chiang Mai airport to return back to Canada, the lady told me I would be unable to fly into Tianjin because, according to her, there is a restriction when transiting through that city, and it requires a Chinese visa. So now, I'm considering what my best options are... I'm thinking of going into the Chinese embassy, but what exactly would I tell them I am applying for? Is there a good chance that I'll be given a visa just to transit through that city? Thanks in advance! If this is in the wrong section, please move it.

Moved to the visas for other countries forum.

Are you transiting airside, or is it a longer stay meaning you'll need to go landside? you might find this helpful travelchinaguide - visa/transit

The Chinese have a visa application centre in Bangkok, http://www.visaforchina.org/BKK_EN/ and they have a facility to seek help via email.

Chinese visas usually cost the same, whether transit or regular, so few people actually go the transit visa route.

If you're Canadian, you're eligible for a multple-entry visa good for ten years (or the life of your passport, if less). I don't know whether the consulate will issue this to you (sometimes they're available only in your home country), but you certainly should ask for it. And having one will eliminate all your worries about getting caught by the many special rules under the Chinese transit-without-visa procedure.

And the advice you're getting seems to be right, since this is what Timatic says:

"Nationals of Canada and USA are not permitted to use the multiple-stop transit within China, if transiting through Tianjin (TSN), Weihai (WEH), Wuhan(WUH), Xi'an (XIY) or Zhengzhou (CGO)."