Is there a best practice remediation for PhpStorm’s warning that void function the_post_thumbnail is used?

The solution is simple, don’t echo the result of that function, there is no result to echo.

echo the_post_thumbnail(array(155,55));

Is equivalent to something like this:

echo '';
the_post_thumbnail(array(155,55));

Functions that begin with the_ in WP don’t return things, they output things. Some of them let you pass a parameter that lets them return instead, but those are the exception, also don’t do that.

The echo is both unnecessary, and incorrect PHP.

So, just use this:

the_post_thumbnail([ 155, 55 ]);

Notice I also swapped the old style array syntax for modern array syntax, and spaced out the parameters.