The template for the Thai evisa is a joke. It's been made to be a cash cow. It's difficult to achieve for the average person and many will fail. When you adding more than one document to an upload it overwrites the previous document. I had to put the documents into a word document then convert it into a PDF format and upload. Many would not have the computer skills to do this. I made an error on the date of issue of my passport? No idea how I could have screwed that up. So I've paid again and I wait.
I'm following the advice of a moderator on the Facebook page Thailand Visa Advice and not this group. An added hurdle is flying out of Canada to Thailand with a longer flight itinerary than your visa, airlines often turn people away. If you have a visa you obtained with the flight itinerary, then you have a good chance of convincing them to let you go. I've experience this and know of others who have too. So it's a little bigger than just covid extensions.
because I left Thailand on Covid extension visas. Thailand is turning away those who actually helped them during the pandemic. I had no idea those visas would be problematic at the time. This could be my last long stay in Thailand, time to explore other places.
Good luck on applying for your 60 day visa. Doing this on line is 12 uploads. I just did it and was rejected for an apparent mistake on the date of issue of my passport. This may have been as simple as a date formatting error such as day month year vs month day year? So I'll need to pay again and do it all over. Its possible I will make this same mistake again. It's little wonder Thailand has fallen to 8th place globally for satisfaction for expats, now behind Vietnam.
I had the same question and recently spoke with with a Thai Embassy. They said, their not bothered about the exit date for a visa. However. The airline taking you to Thailand may turn you away at the airport if your itinerary is longer than your visa. It might be advisable to have a flight out before the visa expires... I'm pondering the same situation and nobody knows what will happen at the airport.