no it’s more complicated than that, you need a full estimate on the letterhead from the Dentist, in my case I asked for a quote for seven crowns to be removed and new ones put in, I asked them to put in a panoramic x-ray, a full cleaning and a check up, comprehensive dental work, not just an appointment, the dentist signed the letter, but my wife and I already have a relationship with this dentist so that made it easier
I went through all this just like you because I’m self-employed, I went around in Circles for days, finally they just asked me if I wanted to switch the category from remote worker to soft power activities, I immediately said yes, I was approved the next day after I got a letter from my dentist in Hua Hin, in retrospect, I should’ve just applied under the soft power category in the first place 
in Canada at the consulate in Vancouver I was not asked for flight or accommodation proof, I did put the address of the condo. We are living at In Thailand, plus our flight information, but no proof was needed