There is one place that impressed me a lot in my last visit to Bangkok, Sandaime! This restaurant is a sushi place that brings all the ingredients they use directly from the Tsukiji Market in Tokyo. The freshness of the fish is outstanding, really hard to find something like Sandaime outside Japan.
Sandaime was one of the best sushi experiences I had in my entire life, check it out if you are going to Bangkok in the next couple of weeks!!