We have a Siamese, she’s very high strung. She loves Oscar and anytime he’s out she wants to be in the middle of it. I let her, as long as she behaves. He will chase her and she will run, which is fine, but as soon as she looks like she wants to turn it around I step in. Even if she’s just laying down and watching him, as soon as she turns on that hunting stare I make sure to snap her out of it. She has of course ended up running at him/trying to chase him, but she never actually tries to engage him in a scuffle. If she chases, he normally just stops running, then chases her in turn. I wouldn’t allow them any contact at all if I didn’t know that she won’t go beyond the “running at him” part, or if I felt like he was scared of her in the least. They are of course never together unsupervised.
I’ve also found treats and clicker training to be highly effective in teaching her appropriate behavior around Oscar. I treat her for any calm interactions, especially ignoring him. I also have her do the tricks we’ve taught her while he’s running around the room, which gets her used to focusing on something else while he’s around.
I agree with MD, if it’s hard for your cat to learn not to look at him as a toy or to be calm around him, letting them have contact might not be a good idea.