no idea about Japan. But yes they should tell you the requirements prior, if they reply at all. However, I would go to Vietnam instead, either HCMC or Hanoi embassy. Many people have found both of those embassies to be quick and easy for DTV applications. Search this group to read some experiences 👍
Is your main concern not having met the financial requirement specifically for "3 months prior" to applying? Or not meeting the financial requirement at all? If the former, note that some embassies do not require 3 months of bank statements. Look into HCMC. In October 2024 I applied there with only one month bank statement and having only met the financial requirement for one day (transferred money to that account the day before I applied). Of course they may have changed their requirements.
Also from my personal experience and from reading other anecdotes, it seems embassies in HCMC and Hanoi are the easiest/quickest ones to apply to. May want to search some info about those ones. E.g. around October 2024 HCMC only required bank statement indicating 500k baht, no need for 3-6 months. I gave a 1 month statement and had transfered money in the day prior to application. Met the requirement only for that day
Search this group. Most of your questions can be answered with little difficulty.
Main question really seems to be whether your remote job "counts". Why wouldn't it? Are you leaving something out about it in your post? Do you get paid? Do you have a contract?
not sure of your source. Been told after 3 months need Thai license. Don't want to argue the legality roadside with a Thai officer. In any event, this doesn't affect whether a 5 year license would matter. Temporary 2 year should be fine for most.
because In Thailand, while an IDP is technically valid for one year, its validity for driving within Thailand is limited to 90 days from the date of each entry. So for staying longer it's recommended to obtain a Thai license.