Best to drop into immigration and ask exactly what they require. Don't usually need to wait long to ask a question and it seems not all offices ask for exactly the same things.
I've used the multiple entry from Canada many times. I typically get my 60 days which is usually 57 days and a visa extention. I then do an out and in on a land border and receive another 60 days. If your still short do another extension. This is the most expensive option!
they never ask on the Thai end if you have a visa. It's prior to leaving your home country. I've had this problem with Air Canada with an itinerary longer than my visa allows.
even in Hua Hin the air quality can be bad at certain times of the year. With covid wearing a mask was really helpful for me. Never as bad as Chiang Mai and typically short lived.
I spoke with the Thai Consulate in Vancouver and they wouldn't accept a land boarder exit and require a paid flight itinerary... I'm not sure why at this time things are being made so difficult?
These stories makes a person wonder if the actual want long stay tourists? Tourists travel about and don't always know where your going? Often traveling to places recommended by other travelers.