The Dehong Dai script developed from a script known as Old Dai, which developed from a script called Baiyi. The Dehong script is used mainly by the Tai Ne/Le people in the Dehong region in southwestern Yunnan province. It has also been used on occasion by the Jingpo people.
Originally tones were not usually marked in the Dehong Dai script, and there was no distinction between some vowel sounds. In 1956 a revised version of the script with tones indicated by diacritics was officially launched, and in 1988 in another revision the tone diacritics were replaced by tone letters.
Dehong Dai, a Tai language with about 443,000 speakers mainly in Dehong Prefecture of Yunnan province in the southwest of China. It is also spoken in northern Vietnam, France, Laos, Myanmar, Switzerland, Thailand. The language has many names, including Tai Nüa, Tai Neua, Tai Le, Chinese Shan and Chinese Tai.
This text uses the tone diacritics
This text uses the tone letters
Source: http://www.seasite.niu.edu/tai/TaiDehong/, with adjustments by Ian James