Sorry, they are showed characters as a few is just square boxes, for all the font sizes and types, can you please fix it, for all three fonts of Sans Lao, Sans Lao Looped, and Serif Lao?
Have you checked to see if the versions of Noto Sans Lao, Sans Lao Looped, and Serif Lao available to download at the Google Fonts web site have the same error?
Welcome to the community! Apologies for the delay. I'd like to inform you that this is the issue with the preview only and our team is working on this. The character will display correctly on your work.