most mp3 players can not do this specifically, however you can do it.
the files are generally automatically sorted by alphabetical order. so even if you add them to the folder in the order you want. it wont matter.
so one workaround is to label the start of each file name with a, b, c, d, e, f, g, in which ever order your partner wants.
however this may NOT work with numbers - some mp3 players and computers consider 11 to be before 2.
the numeric order on a computer/mp3 player would be "1, 10, 11, 12, 13, 2, 3, 4, 5, 6, 7, 8, 9"
there is not numeric order - so it will only work alphabetically.
most mp3 players will allow you to set up a play list - so if your partner wants to be difficult then the method above is one way to help the.
... in the same order? My partner wants an MP3 player that will let him write the files he wants to play to a folder in a specific order and then have them play back in exactly that order. (Why doesn't he just make a playlist? I don't know. But it's this is what he wants.) Can anyone recommend an MP3 player that will do this? Mine won't, but I don't even know if this is a common or uncommon function on MP3 players.