Couldn’t type Thai Language in Acrobat Pro on Ipad Pro

Despite I installed all the Thai fonts on Ipad, and the fonts showed on Acrobat, what I typed in Thai didn't come out as it should be. The font's actual appearance didn't show, and the vowels came up incorrectly, forms of errors as you can see despite you knowing the language, as this photo attached

Please help me solve the problem. Thanks.

Varis