A Thai Soundex System Vichit Iorchirachoonkul National Institute of Development Administration, Bangkapi, Bangkok 24, Thailand. Introduction Name search may be carried out in various ways. Name search in the sense of same spelling finds little practical use mainly due to the fact that in most natural language variant spellings zyxwvutsrqponmlkjihgfedcba may result in similar pronunciations. Furthermore, poor hand-writing and voice transmission may be additional obstacles to name search based on the assumption same spelling. Thus, the soundex method developed by Ode11 and Russell [ 1, 2 1, which attempts to group variant names of similar pronunciation, is very popular for practical application of name search. The BNF of Russell soundex may be defined as follows. eoundex"code) ::f ~ette~'+.gi+ ~igi~~<&gi+ 4ettep ::= A\BICID/ ...IWIXIY/Z1 Briefly the Ode11 and Russell soundex algorithm, details of which may be found in [l, 23 increases the chance of finding a name by retain- ing the first letter in the surname to reflect the sound of the initial consonant as the letter in the code. The following letters in the sur- name less vowels, w and h are classified into 6 groups in views of final consonants with slight adjustment and each group is given a digit as its code accordingly. In Thai name search there is no exception. The Ode11 and Russell soundex algorithm may not be directly applied to the Thai nams search. The structure of Thai language is completely different from the English structure. In the Thai language there are 72 characters appearing at 4 different levels which may be grouped as follows. 243