amp post Thumbnail Size problem

Hello @immmukeshpatel

Thank you for contacting us, you are using native HTML which adds custom styling to your image based on your height attribute.

It seems you are using native <img> tag, which adds some CSS that adds images with height so you see stretched-out images.

I will recommend by unchecking the native html support

goto AMP->Settings->Other-> uncheck “Use native HTML image tag“

Once you change settings clear your site cache and recheck AMP page.

OR you can use the following code in your child themes functions.php or in a custom plugin

add_action( 'amp_post_template_css', function ( $amp_template ) {
	// only CSS here please...
	?>
	figure.amp-wp-article-featured-image img { height:auto; }
	<?php
} );

Let me know if that fixes your issue.

I have created a Github issue to address this issue