The Pro16PNP cards with the ALS100 chip are low profile :

The CMI8330 based Audio Excel AV310, it's also a few of ISA cards with fully working SPDIF I/O in DOS. Like the ALS100 it's one of few ISA cards that emulates Sound Blaster 16.

Smallest ISA sound card? Is it this ES1869?
https://www.alibaba.com/product-detail/ISA-2- … 0013273476.html
https://fccid.io/M4CS0037

Is FCCID stolen from this card? FCCID si unreadable:
http://www.plccenter.co.uk/Buy/ISA/M4CS0037?redirect=true

BTW super slim PCI sound cards:
4ch ES1938:
https://www.alibaba.com/product-detail/4-chan … 0484057724.html

4ch CMI8738:
https://www.alibaba.com/product-detail/CMI873 … 0385987238.html

6ch CMI Startech:
https://www.startech.com/Cards-Adapters/Sound … s/~PCISOUND5CH2

Some OPTi based ISA cards were low profile too.
Search for Expertcolor MED3931 if you want red colored card:
http://www.flaterco.com/kb/audio/ISA/index.html#OPTi931
similar PCB design: http://www.dba.dk/lydkort-skod-til-samler/id-1028175583/

two more cards
http://hattix.co.uk/hardware/index.php?page=sound.html

ALS120

and low profile CS4235

If You cut-off gameport 😀

Wow, these do exist. Years ago I was searching for a low profile ISA sound card, after having no luck, I swapped for a different case.

Another find, true low-profile card with Crystal chip and gameport bracket . Now replaced CS4235 with CS4239:
http://www.ebay.co.uk/itm/221830050330?clk_rv … 8585&rmvSB=true