The requirement for a return or onward ticket when entering Thailand via Visa on Arrival (VOA) or under a visa exemption is largely dependent on the airline policy. Some airlines may request proof of a return ticket, while others may not. At immigration, the required documents generally include a passport, visa (if applicable), and boarding pass. Experiences vary, with some travelers reporting never being asked for a return ticket.
YES, it's posted at immigration. If TR visa NO, possibly visa exempt. There are two lines at immigration for foreigners. One for VOA and one for Foreign Passports. The line for foreign Passports only askes for Passport, eVisa and Boarding pass. It too is posted. I have NEVER been asked by an airline for my departure ticket. Other's say they have but it really isn't their responsibility. They are not immigration. I arrived on a TR visa with a one-way ticket. Had to get a round-trip ticket for the eVisa app but cancelled within 24 hrs and got my money back.
OK then if you’re coming for less than 45 days you don’t need a visa. Long haul from Canada almost certainly your airline will want to see a return/onward ticket within those 45 days.
The ask:thailand community, consisting of multiple Q/A groups with over 100,000 members, powers this platform. It is not an official government resource. Our members actively contribute to this resource, and while we strive for accuracy, we cannot guarantee its complete reliability. Assistance to travelers is provided as a community service.