Generally, Photoshop has the problem that you see Khmer Unicode is not working.
You can fix the problem by going to change in the application options.
Try to follow the instructions as below.
Open Photoshop and go to Edit Menu >Preference >Type and make sure you choose text engine options World-Ready Layout (for photoshop 2020) or older versions of Photoshop, you just Select Middle Eastern and South Asian.
Next, you must check in Window > Character and Window > Paragraph.
- In Window > Paragraph, make sure you choose and tick on Worl Ready Layout and Middle Eastern Features.
- in Window > Character, make sure you choose khmer language
after you configure with that, please check Type > language options > Middle Eastern Features (you will see tick icon here)
Then restart the application and check if it works or not.
the result:
