ThaiEditBench: A Mechanism-Typed, Length-Stratified Benchmark for Thai Orthographic Error Correction

Nutchanon Yongsatianchot, Piyalitt Ittichaiwong, Kanyakorn Veerakanjana


Abstract
Thai is written without spaces between words, and its spelling depends on tone marks, silent consonants, and the transliteration of many loanwords. Each of these is a common source of misspellings. We present ThaiEditBench, a benchmark for correcting Thai spelling errors at the character level. It has three components: (i) a six-class taxonomy that types each error by the part of the spelling that goes wrong, plus an etymology tag; (ii) three length tiers (sentence, paragraph, and page) that test whether a model stays accurate over long, mostly correct text; and (iii) a contamination-robust construction, in which naturally attested misspellings are injected into clean text, so the corrupted passages do not appear verbatim in the source corpora. Because the errors are injected, the gold corrections are exact, and a blind two-annotator study measures how reliably the taxonomy can be applied. Grading is at the level of Thai character clusters, with span-based matching adapted from ERRANT. We evaluate 16 models and find that (1) under the benchmark’s conditions, a model that locates an error almost always fixes it correctly, so what separates models is detection; (2) the evaluated Thai-adapted models do not lead the strongest general models; and (3) in long, mostly correct passages, weaker models accumulate over-edits that pull their scores far below their sentence-level results. On real errors mined from Wikipedia edit history, scores are somewhat lower, but the model ranking largely holds.
Anthology ID:
2026.aacl-short.17
Volume:
Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 2: Short Papers)
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venues:
AACL | IJCNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
211–225
Language:
URL:
https://aclanthology.org/2026.aacl-short.17/
DOI:
Bibkey:
Cite (ACL):
Nutchanon Yongsatianchot, Piyalitt Ittichaiwong, and Kanyakorn Veerakanjana. 2026. ThaiEditBench: A Mechanism-Typed, Length-Stratified Benchmark for Thai Orthographic Error Correction. In Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 2: Short Papers), pages 211–225, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
ThaiEditBench: A Mechanism-Typed, Length-Stratified Benchmark for Thai Orthographic Error Correction (Yongsatianchot et al., AACL-IJCNLP 2026)
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PDF:
https://aclanthology.org/2026.aacl-short.17.pdf