  This report presents the annotation guideline for LST20, a large-scale corpus
with multiple layers of linguistic annotation for Thai language processing. Our
guideline consists of five layers of linguistic annotation: word segmentation,
POS tagging, named entities, clause boundaries, and sentence boundaries. The
dataset complies to the CoNLL-2003-style format for ease of use. LST20 Corpus
offers five layers of linguistic annotation as aforementioned. At a large
scale, it consists of 3,164,864 words, 288,020 named entities, 248,962 clauses,
and 74,180 sentences, while it is annotated with 16 distinct POS tags. All
3,745 documents are also annotated with 15 news genres. Regarding its sheer
size, this dataset is considered large enough for developing joint neural
models for NLP. With the existence of this publicly available corpus, Thai has
become a linguistically rich language for the first time.
