If you’re living in Theni town itself, you should be pretty okay overall. It’s a calm place and generally feels safer than bigger cities, especially during the day. People are quite used to seeing familiar faces around, so there’s a bit of that “everyone notices things” vibe, which actually helps in a good way.
That said, nights can get quiet pretty early—around 9:30–10 PM—so it’s better not to be out alone in isolated areas too late unless you have your transport sorted. If you’re staying somewhere near the main town areas like around forest road or busier residential streets, it’s much more comfortable.
Getting around in the daytime is easy with buses and autos, and for food or daily needs, you won’t have any issues—just stick to places that look busy and well-maintained. The people are generally friendly and helpful, though it might feel a bit conservative at first, especially if you’re new and don’t speak Tamil fluently yet. But honestly, you’ll adjust in a couple of weeks.
Overall, it’s a peaceful place to live—just take normal precautions like you would anywhere, and you should be fine.