1.) Generally speaking, it is much more "easy and straightforward" to apply for a DTV at a Thai Embassy/Consulate nearby Thailand:
Vietnam, Cambodia, Indonesia, Philippines, Laos, perhaps Malaysia, etc.
2.) Even at Thai Embassies/Consulates in some OECD Member Countries, the overall process could also be described as "easier and more straightforward", such as:
Australia, UK, USA, etc.
3.) Nevertheless, curious about field reports/experiences of applying for a DTV at the Thai Embassy in Tokyo
4.) From new information on the Website of the Thai Embassy in Tokyo, it seems that non-residents of Japan PERHAPS may be able to apply for a DTV E–Visa at Tokyo, as the stated evidence for "non-residents of Japan" is:
Entry Stamp into Japan showing the Passport Book #,
e.g. older versions of USA Passport Books do not have the Passport # on every page of (older) USA Passport Books
5.) Also, even though all Thai Embassies and Consulates accept and issue E–Visas via the Thai eVisa website, the Thai Embassy in Tokyo has a "Preliminary Consultation" specific for DTV E–Visa applications BEFORE submitting a DTV E–Visa application on the Thai eVisa Website