I want to apply Thai text to LED text effect.
But it doesn't recognize my Thai font.
I can type my text in Thai.
After running, the result is a blank space...

Last year I posted a solution for your case. But you missed it I believe: https://forum.reallusion.com/FindPost406037.aspx
Again it is not easy, but doable. Download that PNG sprite map and add remaining 39 letters from Thai alphabet.
As I explained, you'd need to use 2 rows of text (one for top diacritics and next row for letters).

Note: You may not use LED Text PopcornFX, because it does not support multi-line text. All other text emitters do support it I believe.

In general it would be a good idea to have a separate thread, where people can share sprite files for different languages/fonts.