From https://github.com/PyThaiNLP/pythainlp/pull/728, It remove all model that trained from LST20 and It will remove pos_tag from LST20 corpus. I think I will replace with Blackboard Treebank. Blackboard Treebank: https://bitbucket.org/kaamanita/blackboard-treebank/src/master/ (CC-BY 3.0)