All the cheaper flights to Canada go through the US these days. I wondered how complicated it is to get a transit visa for my wife (Thai) in Chiang Mai. She had one before, but it was a long time ago. And how long does it take?

So, wait times are pretty long these days to get a visa appointment (a couple of months) but are coming down.  However, applying for a transit visa is a waste of time and money -- she should apply for a tourist visa.  The qualifications are the same and the benefits of one over the other are clear.

 

Depending on when she had her last visa, and what kind it was, she may be eligible for renewal by mail.