Thai speech processing technology: A review

This paper presents a comprehensive review of Thai speech technology, from its impetus in the early 1960s to 2005. Thai is the official language of Thailand, and is spoken by over 60 million people worldwide. As with Chinese, it is a tonal language. It has a spelling system using a Thai alphabet, but has no explicit word boundaries, similar to several Asian languages, such as Japanese and Chinese. It does have explicit marks for tones, as in the languages of the neighboring countries, Laos and Vietnam. Therefore, with these unique characteristics, research and development of language and speech processing specifically for Thai is necessary and quite challenging. This paper reviews the progress of Thai speech technology in five areas of research: fundamental analyses and tools, text-to-speech synthesis (TTS), automatic speech recognition (ASR), speech applications, and language resources. At the end of the paper, the progress and focus of Thai speech research, as measured by the number of publications in each research area, is reviewed and possible directions for future research are suggested.