Within the Thai language, there is only one way to pronounce a word or set of letters. Unlike english where a word can have multiple pronunciations (poe-taye-toes and poe-tah-toes).

As well, each of their vowels have 2 distinct pronunciation lengths. Best described by a 1/2 length and a double long sound. (A and O, being 2 of the vowels) ((When being misunderstood that I went to Hat Yai, I learned to use the double length vowel 'Ah' to make it Haaat Yai and it was instantly understandable.)) They also have what I call assumed vowels. You have to know a sound (that we associate with vowels) will link the 2 consonants together. These have a normal length vowel sound. That gives us 3 lenghts. 1/2, normal, and double length sounds for vowels.

Thai - ไทย - sounds like 'Tai' (no H or th sound)

Koh, in Koh Samui - เกาะ สมุย - sounds like an interupted 'KO'.
This is an instance where the 1/2 lenght vowel O is used. For the english speaker to sound it out properly, it is cut off so abruptly that the word/sylable sounds unfinnished.
The symbol used here is actually a spoken 'G' and should really be written 'Goh' (but the english would then say Go, as in Stop and Go, which is incorrect).

Pattaya - พัทยา -'Put (or pat) taie Yaah' (2 normal lenth vowels, followed by the double length final vowel)

It's nearly impossible to explain Thai sounds with English characters. I'm sure other Thai speakers will chime in. This is my interpretation for the moment.