Vegetarian food is available rather easily here in Malaysia. Most indian cuisine outlets would have a section for vegetarian. As for Malay cuisine, you are able to select dishes like Ulam (Raw vegetables with Sambal - Pounded Chili, tomato and lemon juice). However, you need to check if some sambal would contain shrimp paste.
As for Chinese cuisine, there are selected food outlets that specialises in vegetarian dishes. In short, it is not an issue to look for malaysian dishes that are vegetarian.
Hope this answer your question. Thank you and have a good day.