Sounds good. I think that they they will slowly require this everywhere so I recommend you go to the embassy mentioned by the other posters as soon as you can. The Thai government is trying to avoid people living with no income or working illlegally in the territory hence the creation of the DTV visa and the request for proof of income in more and more embassy.
Passive income works. Proof of income usually can be pay slip, statements, outlined bank transactions coming into your account. You should write a brief letter explaining the source of your income and how you are presenting the proof.
Permanent address must be your home in New Zealand. I strongly advise against putting your Thai address for permanent residence. There is a section where they ask you to specifically write your address in Thailand which is supposed to be your "intended" address.
A sponsorship letter from an employer seems like a viable option for a case like this since your friend is not incorporated or freelancer but an employee. Sponsorship in immigration usually refers to either employers (for getting a work permit usually, so a bit of different scenario) or family. Best to email the embassy and ask for clarification. If you do not receive an answer within your acceptable timeline and can not provide any proof of the 500k, have your employer draft a sponsorship letter detailing their level of financial support to you.
It says that you should print it out or must print it out ? Let me know and I'll acknowledge my mistake.
Regarding phone, if you have lived long enough in Thailand, you should know that they use their phone more frequently than westerners and QR culture is much more developed there. They can for example withdraw money just with there phone and no bank card, something that has barely started in the West.
Embassy in Canada can take 1 business day and some embassies like France will take 20 business days. This is the range so far, not sure if somebody has seen longer posted time for an application filed correctly.