You should definitely stick to something meant to be served cold, like the peanut/sesame noodles mentioned above. Anything hot will get mushy fast if made for a large crowd.
This is a Thai dish that is common there, but not frequently seen in US restos:
https://www.seriouseats.com/kanom-jeen-nam-ya-thai-fish-curry-rice-noodles-5199040
Obviously, to veg-ify, you’ll need to make some subs. Swap tofu for the fish, light soy sauce (the Thai kind, not Kikkoman) for fish sauce, and skip the dried shrimp (or you can sub a small bit of miso for the salty umami). The curry is kept hot to the side, and spooned over cold noodles & veg by each person, as they serve themselves.
Another option would be Gado-Gado served with noodles (I like to use udon) in addition to the typical salad items.