Hi Pixie and welcome. I'm a certified therapist too and I used to teach English in Bangkok. Jobs are limited to foreigners with teaching ESL being the most common job. I can't speak for Samui, but there are quite alot of jobs that don't require the PGCE, just the TESOL course along with a degree.
If you plan on teaching in Thailand it's good to take the course there to give you an idea of what to expect.