Understand Windows OS basic operations only allows one 1 active (in-focus) app at a time, even with 2 monitors (which is what I do with PPT and OBS, and a PTZ camera control s/w). So, if you click on OBS to control it, PPT, by definition, won't be in focus. If your remote is a simple one that only works on active window in the Operating System not a specific application then no - it won't work the way you are asking.
However, there are other approaches
Assuming, a person remote from keyboard insists on controlling PPT, then options would be
- run PPT on dedicated computer, and probably using NDI send its output to other PC with OBS [I'm not a fan of this, but one approach]
- another would be to control OBS from PPT (using websockets). This assumes static choices, like slide change, move camera or start music, or change camera source, etc
- IF there is a need for an OBS operator to have flexible control of OBS, and PPT needs to be on same PC as OBS, then your basic answer is that you'll need to use a remote control for OBS (something talking direct to OBS, presumably websockets, such that OBS doesn't need to be active window so simple pointer remote will work for PPT).
Maybe there are other approaches, the above is off the top of my head