Lets say I have a hosted zone - hostabc.com and have an SSL Acm on that hosted zone.
However when I access to some of the assets static.hostabc.com/style.css. The address url wasn't set SSL on it. How do I resolve this?
Unfortunately, you can't use an SSL certificate with an S3 static website and a custom domain.
I would recommend using AWS CloudFront to handle this. You can point your sub domain to the CloudFront Distribution, which in turn resolves to your S3 static website. You can associate a CloudFront Distribution with an SSL certification in ACM.