Short answers, pulled from the story.
The first known inscription in the Thai script appeared in the year 1292. This script is an abugida written from left to right and records sounds that were already centuries old at that time.
The loss of voiced consonants in the 14th century forced the Thai language to invent a new system of tones to preserve meaning. This linguistic shift occurred between 1300 and 1600 CE and transformed plain voiced stops into voiceless aspirated stops.
The Thai language divides into five distinct registers known as Street Thai, Elegant Thai, Rhetorical Thai, Religious Thai, and Royal Thai. Each register serves a specific social function and reflects the rigid class structure of Thai society.
Khmer provided the largest number of borrowed words to Thai vocabulary with over 2,500 Thai words derived from Khmer. This influence is particularly preponderant in royal court terminology and spans all semantic fields.
Modern Thai uses five phonemic tones identified as mid, low, falling, high, and rising. These tones are essential to the meaning of words and originated from a historical tone split that occurred between 1300 and 1600 CE.