Actually this has nothing to do with decompiling and little with reverse engineering.
What you need to do is to change
Using ResourceHacker you should be able to do just that. The canonical way, however, would be to use the Manifest Tool (mt.exe) which is - depending on the version - included with the SDKs, WDKs or Visual C++/Studio.
Another way would be to strip the resource and place a manifest next to the .exe with the same name, but .manifest appended. I.e. if your .exe is named
foobar.exe then the manifest would be
And actually, thinking about it, this may even work without stripping the existing manifest resource (perhaps give it a try?). I.e. extract the existing manifest resource, place it next to the .exe as explained above and modify the (external) manifest. Then try to start the .exe ...
However, be warned: if your .exe has been signed, your tampering will invalidate the signature. If the software has been prepared to do integrity checking or certain other circumstances apply (Software Restriction Policies, AppLocker) this may lead to the software being unable to run.
If you wanted to achieve this without tinkering with the manifest resource, you can have a look here. This answer details how to enable running a software without elevation by invoking it with a special environment variable set.
Applying this registry file will create an entry named
Run without admin rights (UAC) in the context menu, which allows you to make use of the feature:
Windows Registry Editor Version 5.00
@="Run without admin rights (UAC)"
@="cmd /min /C \"set __COMPAT_LAYER=RUNASINVOKER && start \"\" \"%1\"\""