Dear Shaun,

Thai is very similar to Chinese. In fact, the similarity is strong enough for the Thai language to adopt Chinese writing system (which may actually happened in the past). Idioms and expressions are pretty similar too. If you say in chinese "qu qu lai lai" that woul be "pai pai ma ma" in Thai and it means the same thing (i.e. "comes and goes"). It is pretty easy for Thais to learn to speak Chinese, although learning to write the character will take time. But Thai language is certainly closer to Chinese than Japanese (whose adoption of Chinese characters was tragic). Thai and Chinese don't have tenses, the verbs do not conjugate. Besides, Thai has adopted many Chinese words. 

But in a higher level of use, Thai adopts terms from Sanscrit and Pali which belong to Indo-European family. Most formal words or difficult terms will have roots in sanscrit/pali; it's just like the way technical terms in English have roots in Latin or Greek. Thai writing system is actually designed to assist importation of these Sanscrit/pali terms. That's why there are many redundant alphabets.