Upvote:2
It might, it might not. It depends on the reason for the denial.
All you can do is be honest. If at any point you are asked whether you've previously been denied entry, you need to tell the truth. If it's in paperwork, attach a letter explaining clearly the reasons for the denial. Don't blame the system or the government or whatever, just state the facts of the events and the reasons given by Thailand.
If it's something that Canada decides doesn't affect them, or wasn't too 'bad', they may choose to ignore it.
It's also possible Canada only asks whether you've been previously denied entry into Canada. In this case, you'll happily be able to answer 'no'.
Whatever happens, be honest. If you try to cover it up and they have some data sharing with Thailand or somehow find out from another source that you've lied to them, it's a massive blow to your chances of getting a visa. So be open and honest, and let us know how it goes!