Hi Tara, I've just came back from Thailand after spending 1 month travelling around various places. I would suggest go lite on eating chillies-spices and be careful on which street food you choose to eat at. I also think I have some issues with having Ice in my drinks over there.
I have Diarrhea much more frequent when In Thailand, the toilet trips normally double for me. One little tip I could give you is to make sure you have toilet tissue paper with you as some toilets in shopping malls-supermarkets require you to purchase it before entering. (thats if the machine works) Also some of the toilets are not the same design as here in the western world, some are flush on the floor where you have to crouch, not nice!! Other than that im sure you will have a wonderful time in Thailand, I love it.
I just got back from a few weeks in Australia. My tips:
Eat very light before flying.
Drink bottled water ONLY
Bring Charmin to go... little packages of TP for use.
Find fast food restaurants. There is ALWAYS a bathroom and no one will ask questions
Bring extrea meds