Went there a few days ago after having watched a movie at the Kuenstlerhaus Kino. I was craving good Thai food and because I had been to the "Siam" before (although years back), I thought they'd serve good Thai food. I was mistaken. When I entered a group of Thai women were sitting at the second table from the entrance, chatting away. Nobody greeted me. I said hello, only one of the women (who was NOT the waitress) replied. I went to a table to sit down. Only one other table was occupied with 4 guests (it was about 8pm). I ordered Tom Yam Gung and Green Beef Curry with rice. The soup consisted of mostly (canned?) mushrooms and a few shrimp. It tasted neither spicy, nor sour (like I would expect it). But the greatest disappointment was the "green curry". It wasn't creamy (like I'd think because of the coconut milk used), it was thin and very oily. Besides some beef there were some potatoes, one small piece of red chili (which wasn't spicy) and a few pieces of holy basil and lime leaves. Not at all what I'd expect from a green curry.
The waitress didn't once reappear at my table, asking, if I wanted any dessert. She sat at the table near the entrance, chatting with the other Thai women (who were eating as well - but hopefully better food than the one I was served). When she didn't appear and the guests from the other table wanted to pay as well, one of these guests went to fetch her. I paid and she didn't even say thank you (although I gave her a tip, because it wasn't her who was the cook). I left the restaurant disappointed, having spent 22€ for nothing. I can't recommend this restaurant anymore.