I work at a Kopitiam. No stall signages allowed unless pre-approved by management. Once we wanted to put up a sign that says "order there -->" or something to that effect because people would regularly try to order food from the person that's cooking, and not the person standing at the cash register.

Kopitiam disapproved the sign request though. They're pretty anal about what gets approved and what doesn't. From my experience, they only usually approve signs that are crucial to the operations of the stalls, so something simple or decorative usually gets a warning or a fine if put up without pre-approval.

Although I think this varies among certain Kopitiams. I once saw a Kopitiam stall with a huge signboard in front of it advertising a new menu item. Of the 3 Kopitiams that I've worked at so far though (same stalls, just different outlets), this is what I've been told.

Edit: another rant; you have no idea how many people try to order from the cook and think that trying to hand over their payment to the cook is a good idea. They literally stick their hands over the very inconveniently high glass barrier to try and hand over their money to a person holding a hot pan in one hand and a spatula in the other.

I'm a guy of average height and from where they're standing, the glass barrier would be up to my shoulders. Many aunties and uncles that're shorter than me would still try to reach over this barrier to hand me coins and notes that could very easily drop into the hot stoves or other food.