Masato is indeed a really good sushi Omakase . Last time I went there price was about 5000 thb each , probably higher by now. This is good value actually.
- For Sushi my favourite is not Masato but Masa Otaru in icon Siam. This is the branch of a famous restaurant in Hokkaido, everything is imported from there (while most restaurant got the same supplier from Tsukiji) with a very high focus on seasonal products. Their speciality is a sea squid spaghetti topped with Uni (not your regular uni). They got set lunch at 2-3k if you want to give it a try. 6k for the regular dinner set, you need around 3 hours time.
- For Udon, Komugi is my favorite by far . Their signature is a Siroi curry udon in which they use potato foam. The taste is very similar to what you can experience in Tokyo. Around 300-400 thb.
- For Ramen, well my favorite joint just shut down so I d have to go with Mensho Tokyo on Sukhumvit . They got famous for being the first ramen shop to earn a Michelin star. The strong broth flavour really suits westerner palate. The queue is sometimes very long (over an hour), avoid on the week end. Menya Itto near Grand Hyatt is also very good
- For Yakitori , Toritama in ekkamai is very good and great atmosphere. Great choices of sake as well
- For Yakiniku, Shoutaian in Hotel Nikko serves high quality Wagyu, can be a bit pricey though. Cheaper options and still very good is Ranhichi in thonglor 13.
- For soba, hmm no , everything I tired has been disappointing
- For Tempura, I like to go to Don Don on soi 39, it s a family owned restaurant that s been here forever, they got a set with Udon and tempura for 350 thb, amazing value
About Isao, it's often recommended in westerner and thai forum. It's nice and original but won't really call it a jp restaurant, more like fusion cuisine to appeal to thai people. Very good step up from Fuji though.