Can a Monk use multiple Ki points to get more unarmed strikes from Flurry of Blows in a single turn?

Question

In a recent session of 5e, our monk (4th level, Way of the Drunken Master) was using unarmed strikes, and the DM claimed that she could use any number of available Ki points to increase the amount of unarmed strikes granted by Flurry of Blows by an equal amount (spend 1 point to make 2 strikes, spend 2 points to make 3 strikes, etc.).

I argued that since the Flurry of Blows text says you can make two unarmed strikes as a bonus action, only one Ki point could be spent on this specific feature per turn.

By RAW, how many strikes can be made in a single turn using this particular feature?

Answer 1

You are right, your DM is wrong.

The description of Flurry of Blows says:

Immediately after you take the Attack action on your turn, you can spend 1 ki point to make two unarmed strikes as a bonus action.

That’s it. Nothing about spending more ki points for more attacks. You may spend 1 ki point for two unarmed strikes as a bonus action; you may only take one bonus action per turn.

You can take only one bonus action on your turn, so you must choose which bonus action to use when you have more than one available. (Ch-9, Basic Rules, p. 72)

As a counterexample, the Way of the Four Elements monk has an ability that allows for spending additional ki points to enhance the effect:

Fists of Unbroken Air.You can create a blast of compressed air that strikes like a mighty fist. As an action, you can spend 2 ki points and choose a creature within 30 feet of you. That creature must make a Strength saving throw. On a failed save, the creature takes 3d10 bludgeoning damage, plus an extra 1d10 bludgeoning damage for each additional ki point you spend, and you can push the creature up to 20 feet away from you and knock it prone.

If Flurry of Blows were intended to allow for additional ki expenditure for more attacks, we would see similar wording there.