Should be the same as DLLs - add an export section and define the exports.

i used it one years ago for an updater. running it as EXE it show
something like "process need to be loaded first". note that

1) you cannot LoadLibrary it
2) loader doesnt relocate anything but stuff in the code segment
3) a silently-managed exception occurs on that module at run-time when loading the parent process;
in all cases DllEntrypoint in it will not be executed !! as if the module were flagged DONT_RESOLVE_DLL_REFERENCES.

i am not sure but perhaps this behaviour is possible after some back-compat
down to win95 (because of some system low dll drivers, named as exe).
anyway reason 3) may be a flaw now and should be fixed by MS.

you may think to mark characteristics of the code section of itas R/W/EXEC.
in any case the loader should be allowed at least an explicit read on the reloc section.
with fasm this way
section '.reloc' fixups data readable discardable
then the rest is done, having a double-face module.

Cheers,