Program executed through OS-COMMAND picks up an unexpected value for temporary folder.

When an executable is run from OS-COMMAND it is picking up it's temporary folder path from data stored in the environment key under the PASOE server parameters in the Windows registry entry. This seems to default to the user profile temp folder from the user who installed the Service.

Is there a runtime configuration to change these TEMP and TMP entries? 
Is the proper thing to edit the Environment entry in the registry parameters area?
Is there a way to edit the Environment entry in the registry parameters area for a PASOE service?

The environment created for the registry entry is based on the user environment registering the PASOE instance as service. 

The PASOe instance could be unregistered and set the TMP and TEMP environment variables before registering the PASOE instance again.

For example, if the PASOE instance name is oepas1 and want to define c:\temp for these environment variables, then the following tasks should be run:

proenv> cd c:\OpenEdge\WRK\oepas1\bin
proenv>tcman service oepas1 unregister
oepas1 is unregistered
proenv> set TMP=c:\temp
proenv> set TEMP=c:\temp
proenv> tcman service oepas1 -I oepas1 register
oepas1 service is registered

This will result in the Environment key registry for that PASOE instance to have these two variables with those values given before the register command. This could be done with any environment variable. 

If the PASOE instance is not unregister then the registry variable can be edited from the registry, but since it is REG_MULTI_SZ data type entry, it might get corrupted. Make a backup of the key and edit it manually. It will show a pop message warning about empty strings. Restart the Service and the PASOE instance and test the application.

References to Other Documentation:

Register and manage an instance as a Windows service (service)