He is ftl. He just doesn always utilize his speed. Thor has travelled at thousands of times faster than light in hyperspace. His mjolnir swings have been in canon gone at least twice the speed of light as well. And Thor has tanked Supernova explosions and severely injured beings that are universal+ in power such as Galactus and Phoenix and to a lesser extent Amatsu Mikaboshi. He summoned the dead and brought himself back to life. He's stalemated and outright beaten the likes of Hulk and Hercules in pure physical strength and shattered planets with physical strength alone on panel and stars off panel. All these feats are modern and/or post classic where he is written to hold back and is portrayed weaker. His classic feats are in general even better. He put a barrier around 1/5 of the Universe, pulled the yggdrasil tree which spanned the solar system, way back in the day he collided fists with Herxules and broke a dimensional wall, froze time, absorbed the power to destroy a galaxy in mjolnir his hammer, and beaten the likes of the Silver Surfer on 2 occasions and had the upper hand a third time and so on.