I guess basic ASCII would be too obvious an answer here?

This isn't a conf issue but an issue with non-english code pages and file/directory names.
We'd have to ask Qbix and Harekit to be sure but IIRC, non-english file/directory names aren't supported in DOSBox.
Am I missing something but for the case mentioned would there be an issue with getting rid of the accented a and just using "a" in pajaros?
We would likely have to do some tests to verify how MS-DOS 5.00 handles it. Booting DOS in DOSBox and testing the creation of a directory with the accented a would be the first case.
The more DOS emulation diverts away from how MS-DOS really operates (for so called ease of use) the more distorted things get especially when you go back to using the real thing. It doesn't help when people confuse DOS functionality with the command prompt or other emulators either....

Looking at the conf in the other thread it appears that the game is located at the root of C:\ which shouldn't be done. Games should not be in the root. Assumption of the below could be wrong of course since pepe.bat could be launching the game in another directory, not sure why the cd \ is there unless the implication is the CWD is different and pepe.bat is at the root but I'm thinking pepe.bat is in the game directory and the files are at root of c:\ which is wrong.

[autoexec]
mount C "Pájaros de Bangkok, Los"
C:
cd \
call PEPE.BAT
exit

I'm still not a fan of people using long filenames for DOS emulation for client or host but I understand why lazy people do it. Downside is it lets people forget that MS-DOS only supports 8.3 (not counting TSRs)

To avoid these problems I use basic 7-bit ASCII for all file and directory names in DOS. Everything in UPPERCASE too, just as a reminder that this is DOS not Windows.

That said, it's easy to forget nowadays that there were many many code pages besides 437 in use by DOS systems around the world. There were even special 2-byte ANSI pages for writing Chinese and Japanese.

All this has been swept away by Unicode.

Theoretically MSDOS (and Win9x) works ok with national symbols (80h-FFh) in file/directory names.
Practically -- results are... vary even if you not change the console codepage.
So -- use 0-9, A-Z and 16 non-reserved symbols (or just _). It will works ALWAYS.

P.S. MSDOS reserves 16 ASCII symbols IIRC: " * + , . \ : ; < = > ? [ / ] and |. So you can use ! # $ % & ' ( ) - @ ^ _ ` { } and ~ in filenames. Space is ok too but with "" quotation.

P.S.S. Can't remember a reason for , [ and ] reservation in MSDOS...