I have an appliance that requires 110v, 60 hz that I would like to bring over. Are there step down transformers available that convert frequency as well as voltage? (I'm heading to Samui)

Yes, but if it is motor driven it will not work correctly since an inexpensive step down transformer will not change the hertz ( Hz } so motors will run slower or faster here (don't remember which)

Usually electrical item here in Thailand are relatively inexpensive so importing them and having to deal with the currency change is not really worth it

Care to tell us what type of appliance your planning to bring?

it is a commercial blender. I'm a vegan and my type of diet doesn't fit well with regular blenders (they break fairly quickly). I have a high end unit that I would like to bring

it is a commercial blender. I'm a vegan and my type of diet doesn't fit well with regular blenders (they break fairly quickly). I have a high end unit that I would like to bring

220V => 110V transformers are readily available, they do not however change the frequency.

The usual issue with running 60Hz gear on 50Hz is slow running and / or overheating of transformers and motors. However, since it's a blender and already multi-speed it's likely to have what used to be called a 'universal' motor, these don't run slow (and will actually run on DC with appropriate voltage reduction). Additionally, since it won't be running continuously, overheating is unlikely to be an issue.