I run a thief rogue with two hand crossbows, it's three hits a turn

Action surge is a part of it, but that is only usable once per short rest

If you're using Tasha's then Gunner and Dedicated Weapon let you grab a musket. If your DM lets you use Focused Aim even on attacks you might hit with then it can trigger Ki Fueled Attack easily. It's passable damage plus being ranged means you can take advantage of Monk's mobility to actually skirmish and take cover as opposed to being saddled with the bootleg ranged combat that is typical melee skirmishing in 5e.