Jonn,
Welcome to the board. Hope you will have a great trip in June. Other than Koh Samui, where else are you planning to go?
I think if you ask most BM they will say that have not gotten vaccines before going to Thailand. On the other hand if you consult MD Travel Health (
MD Travel Health - Thailand - vaccinations, malaria, safety, and other medical advice) you will find hepatitis A & B, Tetanus and (for some) Typhoid. I always have my Tetanus shots every 8-10 years, but that is whether I travel or not.
For best and most personal advise you should consult you family physician.