Can't display Khmer characters មោទនភាព

I need to display characters in the Khmer language but when I paste them in a text box the box gets bigger but the characters do not appear. I have installed the Figma agent and that has made my desktop fonts available in Figma. I have no trouble with Arabic and Bengali.

I want to display មោទនភាព

How can I make this work?

Thanks,
Jim