How to Play Sound Files on Client

I want to play reminder sounds on my mobile phone or browser, but I’ve tried playSound or playSteam on my openhab deployed machine or other audio. I want to ask how I can operate to play sounds in browser.

You cannot, openHAB runs on the server, that’s where these commands will take effect.
HABdroid app can’t do that AFAIK, so you would need to use any of the messaging interfaces such as Telegram and install and properly configure that app on your mobile.

While the Android app can’t do this, I think you can do so through your browser. Though you will need to have the browser open at the time you play the sound. See HowTo: Listen & Talk to your Home which I think will get you started.

Or you can use Tasker to poll OH Items periodically and play the sound when they change state.

Of course, Telegram/etc should work as well.