This may be the only Japanese brunch in the Sukhumvit area but if not it’s certainly got to be the best or close to it. What a great selection of food the Tsu and Nami restaurants together put out in the basement of the JW Marriott Hotel on Soi 2.
During the rest of the week these two side-by-side restaurants feature different food. Basically, Tsu is the sushi-sashimi place and Nami serves tempura and teppanyaki. However, on Sunday they join forces and offer diners a wide variety of high-quality Japanese specialties including the above mentioned items as well as a number of other foods such as the delicious oyster creations in the photo at the bottom of the page and interesting combinations of sushi rolls which you can see below. A couple of these are the beef roll and spicy tuna roll which we sampled and enjoyed. 
In addition to the oysters there is also Alaska King Crab legs and the sashimi includes salmon, tuna and Hamachi.
The cooked portion of the buffet includes seafood, beef and lamb teppanyaki and a variety of tempura items also. There is also a selection of seafood that is offered and we tried the butterfish, a particularly tasty white fish, along with some salmon. There’s also a sake bar in between the two restaurant spaces that has a large selection of sake from Japan.
With a price tag of 2,290 baht this is not one of Sukhumvit’s less expensive buffets but if you want quality then this is the place to go on Sundays. 
Tsu & Nami, JW Marriott 
Hotel, Soi 2, 02-656-7700