How to audio out to iPad Pro when connected to HDMI? I have 3rd generation iPad pro. I use USB-C to HDMI adapter to connect my iPad to an external monitor with speaker.

The speaker on the monitor is so bad..I would love to use iPad speaker instead. 

I've looked up everywhere, but it looks like there is no way to disable audio out to HDMI.

Is there a way to turn off HDMI audio out?
Unfortunately not. As far as iOS is concerned, HDMI works at the device level, and responds according to the EDID of the display device - if the display announces via its EDID it handles audio as well, then the iPad will switch audio over to the display device, in accordance with HDCP and the HDMI spec.