No sir I am not using Volt i am using phtml simple form.
/ I want to print error flash message over here/
<div id = 'message'></div>
<html>
<form action='signup/validate'>
UserName:<input type='text' name='username'>
Password:<inpu type='password' name='password'>
<input type='submit' value='login'/>
</form>
Controller Code
validateAction(){
//setflash from here
}
You will need to use the form builder to attach flash messages to form elements otherwise you can just use $this->flash->error('message'); assuming there's an error.