We describe a method of constructing Thai WordNet, a lexical database in which Thai words are organized by their meanings. Our methodology takes WordNet and LEXiTRON machine-readable dictionaries into account. The semantic relations between English words in WordNet and the translation relations between English and Thai words in LEXiTRON are considered. Our methodology is operated via WordNet Builder system. This paper provides an overview of the WordNet Builder architecture and reports on some of our experience with the prototype implementation.