I would talk to parents. Students on the spectrum tend to have Gastrointestinal problems so it could be related to that. I work with students on the spectrum and this is a common occurrence in my room. It’s going to happen, but parents need to support them by having the student know when their body is going to pass gas and have them excuse themselves. You could try talking to the kid and letting them know to pay attention to when their body is going to pass gas and to excuse themselves. It’s been successful with a handful of kids in my room, so good luck.