I have a test page in amp (accelerated mobile page). It is validate as well but the Thai characters are not correctly shown.
AMP validate Thai symbols wrong
Then I have the same page were I substitute
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
Do you realy make a 1:1 copy from index to index2? The characters in source code are different!?
<meta charset="utf-8"> tag as the first child of their head tag."
But your first tag is a style tag!