The knowledge base article suggestions that appear when users start typing their opening message to a ticket, are generated by Kayako's Instant Response System (IRS). With IRS, Kayako is able to search the knowledge base for relevant articles in real-time while the user is drafting a query for submission.
You may enable/disable the IRS from Admin CP > Settings > Tickets > Enable the Instant Response System (IRS)
Sukhpreet Anand