No, there really isn’t.

If you know the languagethe word comes from, you can sometimes make a better guess, like chorus is from Greek, so it’s a /k/ sound there.

But there isn’t really a hard and fast rule. Usually, though, it’s like in church, so guess that way if you have to guess; the sound is /tʃ/.

Wait, I take that back. There is one rule. Words beginning with chr- are always with a /k/ sound. chronological, chrysoprase, Chris. So are words beginning with chl-, like chloroplast.

The imported French word chaise has a softer sound, just a /ʃ/.

I suspect most (maybe all?) words beginning with chy- come from Greek, and so have a hard sound there. They’re all uncommon and rare. For example, chyle is /kaɪl/, < Fr. chyle (= Ital. chilo, Sp. quilo):-L. chȳlus, a. Gr. χῡλός juice (of plants, animals, decoctions).