Coming from the United States, a country where antidepressants and antipsychotics are some of the fastest growing prescriptions, living with mental illness in Thailand can be quite a change. I myself take medication to treat the chronic depression I have lived with for as long as I can remember, and I wondered how the subject would be treated in Thailand. The first thing I discovered was that Thais don't seem to have a concept of depression. Try explaining constant overwhelming despair to someone who barely speaks any English, and you'll soon find how difficult it is. I would imagine that living with bipolar disorder would be even more difficult in Thailand. Many psychotropic medications are used in Thailand for people "with difficulty sleeping". Whether or not this is a euphemism used to save face is up for debate.
Finding your meds is another struggle. Unless you live in Bangkok or Chiang Mai, expect to have to order your drugs from Bangkok. When I first moved to Nakhon Si Thammarat, I went to every pharmacy I could find only to be told that they didn't have the drugs I needed and that they had never even heard of them. I eventually found a pharmacist who ordered my drugs for me. If you take medication for mental illness, make sure you come to Thailand with a nice big supply, because finding a source in Thailand can be a lengthy process. Don't wait until the last minute, lest you discover that the pharmacy needs to order the drug and it will take 1-2 weeks. Running out of a prescription you need in a foreign country is an unpleasant experience, to say the very least. In short, if you're planning on moving somewhere off the beaten path, finding a pharmacist that can help you should be one of the first things you do.