ISO 11940-2:2007

Overview - ISO 11940-2:2007 (Simplified transcription of Thai)

ISO 11940-2:2007 defines a simplified, pronunciation-oriented system for converting Thai script into Latin characters. It complements ISO 11940 (the full transliteration scheme) by providing pronunciation rules and conversion tables for Thai consonants and vowels intended for broad phonetic transcription. The standard is designed for machine-assisted conversion with limited human intervention and relies on authoritative pronunciation sources (for example, the Dictionary of the Thai Royal Institute).

Key topics and technical requirements

• Pronunciation rules applied in sequence: Rules must be applied in order to each word before conversion; many exceptions exist where orthography differs from pronunciation.
• Conversion tables: Mappings for Thai consonants and vowels to Latin representations are specified; preposed vowels (e.g., เ-, แ-, ใ-, ไ-, โ-) are transposed after initial clusters as part of processing.
• No vowel length or tone encoding: The simplified transcription intentionally does not distinguish short vs. long vowels and omits tone marking. Where full pronunciation is needed, the system can be extended by adding long-vowel conversion and tone rules.
• Orthographic handling rules: Detailed rules cover cluster behavior (deletion or transposition of ห and ร in specific contexts), insertion of epenthetic /a/ in certain consonant sequences, gemination rules for syllable-final consonants, and deletion of final vowel signs in specified words.
• Machine-friendly objective: The method is intended for automatic implementation, but human decisions may be required when words have multiple pronunciations or meanings.

Applications - who uses ISO 11940-2 and why

• Library and information services: Cataloguers and metadata specialists use the standard to create consistent romanized headings and improve discoverability of Thai materials.
• Localization and publishing: Translators and publishers apply the scheme for readable romanizations in guides, signage, and editorial content when tonal or fine-grained phonemic detail is unnecessary.
• Software and data engineering: Developers of search engines, indexing tools, databases, and transliteration libraries implement the rules for normalization, search matching, and user input conversion.
• Linguistics and education tools: Computational linguists and language-learning apps may use the simplified transcription as a readable bridge for learners, while adding tone/length processing separately if required.

Related standards

• ISO 11940:1998 (renumbered ISO 11940-1): The full transliteration scheme referenced normatively by ISO 11940-2; use ISO 11940-1 when reversible, precise transliteration back to Thai orthography is needed.

ISO 11940-2 is a practical, machine-oriented romanization reference for Thai-to-Latin transcription where intelligible pronunciation (without tone and vowel-length detail) and consistent data handling are the priority. Keywords: ISO 11940-2, Thai transliteration, Thai-to-Latin, simplified transcription, pronunciation rules, conversion tables, romanization.