ChatGPT agrees with what's been niggling at the back of my mind for days...

You're right to think that *เงินเฟ้อคือคดีอาญา* sounds a bit off because *คดีอาญา* specifically refers to a criminal case, which implies legal proceedings. Since inflation isn't literally a filed case, this translation may feel unnatural.

On the other hand, *เงินเฟ้อเป็นอาญา* is also somewhat unusual because *อาญา* alone typically refers to criminal law or punishment rather than describing something as a crime.

A more natural way to phrase it might be:

- **"เงินเฟ้อเป็นอาชญากรรม"** (*Inflation is a crime* in a general sense)

- **"เงินเฟ้อคือความผิดทางอาญา"** (*Inflation is a criminal offense*, if you want to emphasize legality)

Would you like a translation that keeps it literal, or do you want a version that captures the intended meaning more naturally?