<i>Prathom Ko Ka</i>, a textbook for studying the Thai language. The preface by the Fine Arts Department says "There is no conclusive evidence as to who composed the work <i>Prathom Ko Ka</i> which is printed here, and when it was composed. But, having examined its contents, we are of the opinion that the work is not older than the works <i>Prathom Mala</i> composed by Phra Thepmoli of <a href="https://en.wikipedia.org/wiki/Wat_Ratchaburana,_Bangkok" class="extiw" title="w:Wat Ratchaburana, Bangkok">Wat Ratchaburana</a> and <i>Kap Phra Chaisuriya</i> composed by <a href="https://en.wikipedia.org/wiki/Sunthorn_Phu" class="extiw" title="w:Sunthorn Phu">Sunthon Phu</a>. The two works so mentioned were textbooks used in the reign of King <a href="https://en.wikipedia.org/wiki/Rama_III" class="extiw" title="w:Rama III">Rama III</a> during the early <a href="https://en.wikipedia.org/wiki/Rattanakosin_Kingdom" class="extiw" title="w:Rattanakosin Kingdom">Rattanakosin period</a>."
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กรมศิลปากร (ผู้รวบรวม). (๒๔๙๙). <i>ประถม ก กา</i>. พระนคร: โรงพิมพ์รุ่งเรืองธรรม. (พิมพ์เป็นอนุสรณ์ในงานพระราชทานเพลิงศพนายผ่านพบ บุษยากร ณ ฌาปนสถานกองทัพบก วัดโสมนัสวิหาร ๒๒ ธันวาคม ๒๔๙๙).