I'm not sure what did you really mean by "ssuai" for you. Never mind, but it could be   - beautiful : สวย (suay) [ 수우아이]  if you read following what i write in korean, read it in one shot, and don't accentuate the "이" at the end. For this word, the tone you should pronounce must be deep, if not, it would be  - unfortunate / bad luck / unlucky : ซวย (suaiii) [수우아이 ]  These words seem quiet similar or maybe the same for foreigners but in thai, these words aren't spelled in the same way, and the tone you should pronounce for this one must be soft.  - help : ช่วย (shuaii) [ 츄아이 ] for this one, just like the 2 i've mentioned above, don't accentuate the "이" at the end. Soft or deep sound doesn't matter for this one, what's important is that you have to accentuate the last syllable Like,  추 (normal) 우아이 (accentuate) By the way, when i say that you shouldn't accentuate the "이" at the end mean that, you shouldn't read it like  추/우아/이 , just go with the flow, I'm sure you get what i mean hahahah. Hope it helps you a bit.

Tone in Thai language refers to a change in the pitch of a syllable during its pronunciation. In Thai, every syllable is pronounced in one of five tones: low, mid, high, falling, or rising. The tone must be spoken correctly for the intended meaning of a word to be understood. Since every word has a particular mandatory tone, we say that the Thai language has obligatory lexical tone. Enter "ปา ป่า ป้า ป๊า ป๋า" into http://translate.google.com then listen to the audio. These are five words that have different meaning. Many foriengers may not be able to distinguish the five sound which is O.K.

Here are some tools that can help you understanding (but monosme already gave you all tips) or training yourself to pronunce them : - videos of people on the internet teaching thai tones (5 tones for middle consonants and 3 tones each for both upper and lower consonants) - http://translate.google.com : just download thai keyboard and type in the words monosme gave you : Google can pronunce them for you :)