You bet! After creating the post you can sticky and lock the thread from the Bravenet Message Form Service Manger.
Make sure you are logged into your Bravenet Account and click on the Message Form.
From here you can create the thread - or if you have already - click on the thread you want to sticky/lock. At the top right of your thread you will see the sticky and lock options.
Sticky makes your thread go to the top of the board and lock makes it so no one can reply.