Does Martial Arts Damage Apply to Ranged Attacks with Monk Weapons?

Question

Inspired by an answer to What is the Attack Roll for Deflect Missile?.

The Monk's Martial Arts feature states that monk weapons are, "...short swords and any simple melee weapons that don't have the two-handed or heavy property." (emphasis mine)

For the purposes of my question, I am assuming a 17th level Monk, so that the Martial Arts damage die is 1d10.

My question is that when making a damage roll with a weapon that can be either melee or ranged, like a dagger, which damage die do I roll on a hit for a ranged attack? I am assuming this uses 1d4 because this isn't a simple melee weapon anymore, but a simple ranged weapon based on the definitions for melee and ranged weapons as defined on page 146 of the PHB:

"A melee weapon is used to attack a target within 5 feet of you, whereas a ranged weapon is used to attack a target at a distance." (emphasis from the PHB)

Answer 1

The weapon is still a simple melee weapon, even when you throw it to make a ranged attack.

The weapon's position on the table tells you what type of weapon it is. Since it's a simple melee weapon, it's a monk weapon. Since it's a monk weapon, you can use your martial arts die for its damage instead of its "natural" damage die.

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See also Are weapons with the "Thrown" property considered a "Ranged Weapon" for the purpose of sharpshooter? for more on how we treat a melee weapon when thrown.

Answer 2

You are conflating two seperate ideas

Weapons are either melee or ranged as defined in the table on p.149.

You can use either type to make a melee or ranged attack as defined on p.195.

These are not the same thing

That is, you can use a melee weapon to make a ranged attack - if the melee weapon has the thrown property (e.g. dagger, handaxe) then it operates as normal, if it doesn't then it uses the rules for improvised weapons on p.148. This is also the case if you throw an ammunition property weapon if, for example, you throw your crossbow at someone because you have run out of quarrels.

Similarly, you can use a ranged weapon to make a melee attack - these are always improvised weapons (even the dart and the net) because they are not designed or balanced for hitting people while held.

Note that improvised weapons are always melee weapons: never ranged weapons. Therefore melee weapons are always melee weapons irrespective of the type of attack but ranged weapons become melee (improvised) weapons if making a melee attack.

Features can trigger off either the type of weapon or the type of attack. For example, the duelling fighting style (p.72) is triggered by the type of weapon, throwing handaxes gives +2 damage as does throwing battleaxes (but not greataxes because they need two hands).