In Thailand it may be a problem. I was layman, living in temple. I could manage to keep vegeterian diet by eating only fruits and rise.
But it was big temple, so they have plenty of fruits, I do not know how is the situation in other wats. In Sri Lanka, as far as I know, there are quite a few vegeterian monks, and they have no problem with it. Sri Lanka is in range of Indian culture where vegetarian diet is obvious thing, while Thailand is rather more under China influence, and there vegerarian diet is something unusual.
The man who wants to avoid grotesque collapses should not look for anything to fulfill him in space and time.
Nicolás Gómez Dávila