Mr. Lam's henchmen may look tough, but they are often easy victims. They are often armed with a single pistol (rarely a rifle) and somewhat weak and slow. They primarily stand upright and fire with their weapons, hardly (if ever) dodging gunfire. Their strength comes in their numbers, and having multiple henchman shooting at Hana at once means trouble.
Try to sneak up on henchmen by crouching while walking toward his back. Tagging them once with a hand-to-hand weapon will kill a henchman in one swipe. If henchmen spot you, continuously use the roll maneuver to avoid gunfire until they need to reload. From there, take out your gun and fire away.