Philological connotations among various manuscripts of Xianluoguan Yiyu

Xianluoguan Yiyu is a series of Siamese-Chinese vocabularies compiled by the Ming and Qing government for translation or interpretation teachings. In choosing transcription characters, the compilers emphasized the agreement on initials and main vowels more than distinctions between voiced and unvoiced consonants. Various manuscripts reflect some phonetic characteristics in different periods during two centuries, in which it is proved that the sound changes of ʔb- > b- > m- and ʔd- > d- > l- were completed no later than the later period of the 17th century.