How to resolve Character encoding failure in Thai language files from Adobe InDesign to PDF?

I have tested Accessibility on Thai language PDF file and faced the Character encoding issue while doing Accessibility check. I have checked the InDesign file regarding font and combined Unicode characters. All fonts are embedded and looks good in design file but when I export the PDF file, I have faced this issue in PDF only.

Copy/Paste and Search option also works fine in the design file but after exporting the PDF file these options are not worked and produce junk characters.

Is this something limitation in Adobe Acrobat or else please provide a solution to resolve this isse.