Hi Wayo,

Your code:

* See Bold Font at last word : position="after" it is wrong that used in xpath not domain.

<record id="saymeh_view_order_form" model="ir.ui.view">
    <field name="inherit_id" ref="sale.view_order_form"/>
    <field name="model">sale.order</field>
    <field name="arch" type="xml">
        <field name="partner_id" domain="[('customer','=',1), ('parent_id', '=', False)]" position="after">
            <field name="vehicle_id" />
        </field>
    </field>
</record>

Solution:
    * Syntax for domain : domain="[('FIELD NAME'),'OPERATOR',VALUES]"
    * you can set domain as per your need that used to filtering record values.
Like:
    <field name="partner_id" domain="[('customer','=',1), ('parent_id', '=', False)]"/>

Thank You.

Thanks a lot buddy. It woks perfect. 

Blessings