tinymce-docs-4x/_includes/configuration/visual.md

visual

This true/false option gives you the ability to turn on/off the visual aid for borderless tables. If the border of a table is set to 0, then TinyMCE adds a dotted line around the table by default.

Type: Boolean

Default Value: true

Possible Values: true, false

Example:

tinymce.init({
  selector: "textarea",  // change this value according to your html
  visual: false
});