Would you use "tu" or "vous" with the following person?

The choice between "tu" and "vous" depends on the context and your relationship with Thomas.

- Use "tu" if you are on familiar terms, such as with a friend or someone younger.
- Use "vous" if you are being formal, addressing someone you don't know well, or are in a professional context.

Without additional context about your relationship with Thomas, it's hard to definitively say which to use. However, if you are unsure and want to err on the side of formality, "vous" is the safer choice.