Reference-Grounded Data Curation for Instruction-Following Thai-English Machine Translation

Thodsaporn Chay-intr, Krittapad Harnchang, Mahannop Thabua, Kobkrit Viriyayudhakorn, Thanaruk Theeramunkong


Abstract
Instruction-following machine translation (IF-MT) requires respecting prompt-level rules on terminology, formatting, and register. Rule compliance typically trades off against translation quality, a tension that general-purpose IF data augmentation methods do not address. We propose Reference-Grounded Data Curation, a two-phase pipeline that extracts every supervised constraint from a reference translation that already satisfies it, ensuring feasibility by construction. Phase 1 applies Instruction-Following Difficulty (IFD) scoring to retain the hardest-but-learnable instances from an English-Thai parallel pool. Phase 2 extracts constraints from each reference target and keeps only generations satisfying every constraint, yielding the 1.97M-record Grounded dataset. We fine-tune open-weight bases on Grounded to produce ChindaMT, a Thai-English translation family at 4B, 2B, and 0.8B parameters. Under length-controlled pairwise judging, ChindaMT outperforms or matches every same-size baseline at every tier on both plain translation and under explicit rules, reaching up to a 68.4% win rate against the strongest baseline. The recipe transfers cleanly across Qwen generations. We release model weights, the Grounded dataset, and evaluation suites.
Anthology ID:
2026.aacl-long.54
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 1: Long 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:
1152–1171
Language:
URL:
https://aclanthology.org/2026.aacl-long.54/
DOI:
Bibkey:
Cite (ACL):
Thodsaporn Chay-intr, Krittapad Harnchang, Mahannop Thabua, Kobkrit Viriyayudhakorn, and Thanaruk Theeramunkong. 2026. Reference-Grounded Data Curation for Instruction-Following Thai-English Machine Translation. 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 1: Long Papers), pages 1152–1171, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
Reference-Grounded Data Curation for Instruction-Following Thai-English Machine Translation (Chay-intr et al., AACL-IJCNLP 2026)
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PDF:
https://aclanthology.org/2026.aacl-long.54.pdf