score:5
The website you link to states:
In principle, you should have a legitimate long term residency in Thailand. [...] If you came to Thailand only as a tourist and plan to apply for a Japanese visa, please contact JVAC or the Embassy by phone.
So the answer is generally no, you can't apply in Thailand unless you live there, you will need to return home. Of course you can try your luck and call, but unless there are good circumstances (family emergency etc) I doubt they will let you apply.
My understanding is also that this general policy applies to all Japanese embassies worldwide.