Hello, Jaythai,

What you are asking for seems to be the default behavior. I just tried a Submit Rule validation and the error message showed up under the control. 

See my example below. If this is not what you are looking for, please provide additional details and screenshot.

I added this Submit Rule:

When I click Submit, I get the error under the control.

I am using Classic form, I think you are using responsive form and they both behave differently right? 

You are right. The classic form handles errors differently. You have two options to achieve what you want:

1. If the form is not too complex, create a responsive version. There is no upgrade/convert tool. You will need to delete the classic one and create a new responsive one.
2. Try to use JavaScript to move the errors under the control. I am not an expert on using JavaScript with classic forms, but here is an article that can get you started: https://thrivenextgen.com/enhancing-nintex-forms-javascript/ .