How do I disable/hide the form buttons?

By default, if you have not modified the config.js file, CKEditor loads the full toolbar with its full set of buttons as defined here:

// This is actually the default value.
config.toolbar_Full =
[
    ['Source','-','Save','NewPage','Preview','-','Templates'],
    ['Cut','Copy','Paste','PasteText','PasteFromWord','-','Print', 'SpellChecker', 'Scayt'],
    ['Undo','Redo','-','Find','Replace','-','SelectAll','RemoveFormat'],
    ['Form', 'Checkbox', 'Radio', 'TextField', 'Textarea', 'Select', 'Button', 'ImageButton', 'HiddenField'],
    '/',
    ['Bold','Italic','Underline','Strike','-','Subscript','Superscript'],
    ['NumberedList','BulletedList','-','Outdent','Indent','Blockquote'],
    ['JustifyLeft','JustifyCenter','JustifyRight','JustifyBlock'],
    ['Link','Unlink','Anchor'],
    ['Image','Flash','Table','HorizontalRule','Smiley','SpecialChar','PageBreak'],
    '/',
    ['Styles','Format','Font','FontSize'],
    ['TextColor','BGColor'],
    ['Maximize', 'ShowBlocks','-','About']
];

If you paste the entire above code into your config.js (between '{' and '};', of course!) and remove the buttons you don't need, you'll eventually get to where you want your CKEditor to be..
In your case, you can remove all FORM buttons by simply removing following lines from the config.js after you have pasted the code from above:

['Form', 'Checkbox', 'Radio', 'TextField', 'Textarea', 'Select', 'Button', 'ImageButton', 'HiddenField'],

You can remove one button at a time, or as many as you wish. You will find out that [...] encloses a block of buttons '-' is a spacer and '/' is a new line. Make sure you do NOT modify any of the button names.

Have fun!