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 
I am told all embassies and consulates are moving to online visa application only at the end of October, no more in person visits to embassies or consulates. Each country is very different, here in Canada just the BIO page of passport, no reason to ask for empty pages, that is silly. Also Canada is very expensive, $500 USD or $650 CAD for each DTV Visa, $1300 for my wife and I CAD, or $1,000 USD, not cheap, but great Thai consulate to deal with, very freindly and very efficient and fast, we had our DTV Visa within 2 days, they even called me to change my catagory f rom remote worker to "Soft power activities", and I did not h ave to pay any extra fees, overall great experience, except for teh high cost herre in Canada
I think what they are doing, they only want people who do have enough money to survive in Thailand, Thailand does not want people who borrow money from somebody to make it look like they have enough money, then get to Thailand and have financial problems, I’ve seen it countless times over 25 years,people coming to Thailand that are really bad with finances and don’t have enough money, they caused more trouble than they are worth