If you really want to look for a precedent, go back 12 years. A badminton player went into the stands and hit a spectator (who was heckling him) with his racquet. I am not sure what bwf (or IBF) gave as punishment but am almost certain no ban was given.
Drugs gets you a two year ban. I think a punishment should be 1-2 years as Scorpion1 suggested. But I really think the previous situation of a player hitting a spectator should be used as guidance.
This player is Taufik?