It is illegal in Thailand to use vapors and tbh it winds me up folk smoking them in your face when in their own country's it has to be done outside. I think most folk who smoke them don't give a damn about folk around them.
Take as much as you can in your suitcase that goes in the cargo luggage. I’ve travelled to Thailand many times with medication and had no documentation or declared it. Carry the prescription paper you get from the pharmacy if it’s ever quizzed.