Thai, also called Siamese, is the official language of Thailand, a country in Southeast Asia with a population of 63 million people. However, only about 20 million of the people in Thailand are native speakers.
Thai is a tonal language. Different tones give different meaning, which makes it quite difficult to learn the language in the beginning. In spoken form, Thai is very similar and in fact mutually intelligible with Lao (the language of Laos). Both Thai and Lao belong to the Kra–Dai language family that covers dialects in the area of southern China, northeast of India and parts of Southeast Asia.
There are various dialects of Thai used in Thailand and while scholars and linguists consider these to be separate, albeit related languages, the native speakers tend to perceive it as one language with regional dialects.

‘Corruption’ in Thai vocabulary

Thai vocabulary consists of many foreign expressions, and paints a picture of historical development in the region. The Chinese influence, mainly until the 13th century when the Chinese script was replaced with Sanskrit and Pali scripts, caused there to be a good deal of words from Middle China. Trade relations with the West has also influenced the language considerably. Notably, basic trade-related and religious words were taken over from Portuguese, as that was also the first European nation to arrive in Thailand in the 16th century (words such as padre for a priest, carta for paper or real for a coin, etc.). English has become the most influential language since the 20th century, mainly when it comes to technical, scientific and modern society terms (such as computer, graph, government, technology, visa, taxi, diesel, and even corruption and wreath).

Alphabet includes tone forms

The Thai alphabets were first introduced in the 13th century by an ancient great king. Over time, the characters have changed in appearance. Today the language contains 44 consonants with 42 that are still in use, and 21 vowels in 32 combinations.
Thai words are often – although not always – composed of characters. That means in one single column, there may be up to three characters including consonant, vowel, and tone composed together.
When it comes to transcription of the Thai alphabet into Latin, there is no universally accepted method to follow, resulting in Thai words being transcripted differently. In fact, an ISO standard for Thai-Latin transcription exists since 2003 and is even used by Google Translate, but yet not very common in daily use (e.g. in textbooks or instructional texts).
For this reason, it is highly recommended to learn the Thai script in order to master the language itself.

Consonants:
ถ ท ธ น บ ป ผ ฝ พ ฟ ภ ม ย ร ล ว ศ ษ ส ห ฬ อ ฮ ก ข ฃ ค ฅ ฆ ง จ ฉ ช ซ ฌ ญ ฎ ฏ ฐ ฑ ฒ ณ ด ต

Vowels:
ะ ั า ํ ิ ่ ่ ่ ุ ู เ โ ใ ไ ็ อ ว ย ฤ ฤๅ ฦ ฦๅ

Tone forms: ่ ้ ๊ ๋