While you are in Thailand, it is possible you might need the services of a doctor. First, I want to say that you don't really need to worry about this. Many doctors in the hospitals in Bangkok have studied abroad and their English is very good. Also, you will find many of the top hospitals in major cities to be similar in comfort to 5 star hotels. But, I think it might be useful for you to learn some words or phrases when you visit the hospital while you are in Thailand.

I don't feel well (chun rou suek mai dee)

Chun is informal for both male and female. However, if you feel you should be more polite then males should say "phom" and females "di-chun".

It hurts here (jeb dtrong nee)

The Thai word for hurt is "jeb". Just point to where it hurts!

I want to see a doctor (dtong garn har mhor)

As usual, you don't have to say "I" if it is obvious what you are talking about. The Thai word for doctor is "mhor".

An earache. (buad hoo)

A stomach-ache. (buad thong)

A Sore-throat. (jeb kor)

A fever. (ben khai)

The flu. (khai wad yai)

A headache. (buad hua)

Diarrhoea. (thong sia)

Constipation. (thong poog)

Been vomiting. (ar-jian lhai khrang)