The Thai language, also known as Siamese, belongs to the Kra-Dai language family, which is believed to have originated in southern China around 4,000 to 5,000 years ago. Early Thai-speaking peoples migrated southward, eventually settling in what is now Thailand and surrounding regions. The language evolved from the Proto-Tai language, influenced by contact with languages from neighboring cultures, such as Khmer and Pali, as well as Sanskrit due to religious and cultural exchanges with India. The establishment of the Sukhothai Kingdom in the 13th century marked the beginning of the formalization of the Thai language, with the development of a written script based on the Khmer alphabet.

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Over the centuries, the Thai language continued to evolve, influenced by both internal changes and external factors. The adoption of Pali and Sanskrit vocabulary, largely due to the influence of Theravada Buddhism, enriched the Thai lexicon, especially in terms related to religion, governance, and culture. In the 19th century, King Rama IV and his successor, King Rama V, undertook major reforms in the Thai writing system to standardize it and make it more accessible. Today, Thai is the official language of Thailand and serves as a unifying factor for the country’s diverse linguistic communities, though various regional dialects still exist.