It is hard to say whether it is genuinely the best Thai food in the city but it must must be the as close to a genuine Thai experience as you are going to find just about anywhere outside of Thailand. Koh Phangan, located on the island of Sodermalm, serves up delicious Thai food in a jungle-like, eclectic Thai setting. This is an atmosphere chain restaurants try to emulate but never quite hit the mark.
It will take an hour or longer to be seated but it is every minute worth the wait. Tables consist of individual beach style huts, fishing shacks and private tables made from old tuk tuks. If the unique interior of bamboo and grass walls lit by only colorful strands of lights are not enough to make you feel like you could walk out into a steamy Thai beachfront evening then perhaps the piped in sounds of rainstorms and tropical fauna will.
When visiting make sure to pay attention to the details. Waterfalls, bridges and even a koi pond can be found inside. Thai trinkets, pictures of royalty and other kitschy items adorn the walls. Even the toilets add something of interest.
Stockholm is not short on choices for Thai eating. In fact you probably can not walk ten feet in any direction without hitting either a Thai restaurant or food stall of some variation. However, if you are limited to just one, let Koh Phangan be it.