We have visited Chachawan more times than I can remember, and most recently last night. It serves Issan style Thai food, and every dish is consistently excellent, every time we go. I particularly recommend the Gai Yung, Wagyu Beef Salad, King Prawns and Pork Skewers, but actually, everything is good.
You can sit in the restaurant, or at the open kitchen - sitting at the kitchen counter is a wonderful experience, and the chef will usually engage with you whilst you're there.
You can't make reservations, so it helps to get there before 7pm. However, we have frequently been later than this and usually have a drink in the restaurant next door whilst we wait for our table. It's definitely worth the wait!