"Countries for which passport is valid": just write "All" here
"Purpose of visit": make sure you don't write anything here related to work
A bank draft from RBC for $250 (I got the multiple entry visa), made payable to Royal Thai Embassy. Bank draft is the only payment method they accept
A copy of the one-way flight ticket to Thailand (the official website says you need a return ticket, but I called the embassy and they said one-way ticket is fine)
A prepaid return envelop with my home address filled out
Sent all documentations in Step 1 to the Thai embassy in Ottawa. Make sure you use trackable post and write down the tracking number of the both the envelope going to the embassy, and the pre-paid return envelope you purchased
I got my passport mailed back to me in about a week. Plan for 2 weeks just in case
One thing to note (that I didn't realize, and is very counter intuitive) is that your visa starts on the date they approve your visa, instead of your expected date of arrival. My visa started on April 23rd and expires 6 months from this date, even though I indicated on the application form that I'll be arriving in Thailand on May 29th (and my flight ticket clearly shows me arriving on May 29th). Keep this in mind when you decide when to apply for your visa.