Hide field at ticket creation but view this filed after in read only

When you create a ticket, i want to hide "SLT option" and "Temps de prise en charge", etc...

But after, when i read the ticket, i can't see this information...

I affected this option by SLA and rules directly :

• VIP SLA for VIP user tickets
• Standard SLA for all other ticket and user

It works fine, but i want to hide this option at the creation, but not after for the followed