The book itself tells nothing about the author except that he received an honorary doctorate. So what did I do? I Googled him, of course. Most of the following below is translated from this brief bio.
Nai Kamchai Thonglor was born in a boat on the Chao Phra River, at Tambon Takhian Luean, Amphoe Mueang Nakhon Sawan, Changwat Nakhon Sawat, on May 17, 1906, to Nai Thongkham and Nang Srimueang.
As a boy he studied at Wat Ko Hong School (โรงเรียนวัดเกาะหงษ์). After finishing primary school, he continued his studies at Nakhon Sawan Boarding School (โรงเรียนประจำจังหวัดนครสวรรค์), finishing grade matthayom 3. After that, he became a novice at Wat Thep Sirintharawat (วัดเทพศิรินทราวาส) in Bangkok. He studied Pali, passing parian level 3, then ordained as a monk at the same temple, and eventually completed parian level 5.
After leaving the priesthood he taught Thai at Intharasueksa School (โรงเรียนอินทรศึกษา) and began to earn acclaim. The headmaster at Bangkok Christian College (โรงเรียนกรุงเทพคริสเตียน) noticed his work and invited Kamchai to teach there. While at the school, he began researching methods for teaching Thai and penned a well-known Thai language grammar and many other books.
Kamchai left Bangkok Christian College after 25 years teaching there. The Faculty of Education at Chulalongkorn University then invited him to join their staff, teaching Bachelor's and Master's students. And starting in 1961, he taught the Crown Prince and Princesses at Chitrlada School.
In his later years, Kamchai was also a committee member on the Royal Institute Dictionary Revision Committee. According to this article, he was on the committee when they happened to decide the มุกตลก/มุขตลก issue that I've previously written about. (The phrase was discussed in two meetings on July 19 and July 22, 1985, just a month before Kamchai's death.)
Kamchai married Nang Sawai, and they had seven children together. During his career he received several royal insignia and decorations: Grand Companion (Third Class) of the Most Illustrious Order of Chula Chom Klao (ตติยจุลจอมเกล้าวิเศษ), Knight Commander (Second Class) of the Most Exalted Order of the White Elephant (ทวิติยาภรณ์ช้างเผือก), and the King's Royal Cypher Medal (เหรียญรัตนาภรณ์). He also received the King's Personal Medal (เหรียญส่วนพระองค์ (ภ.อ.)), the Senior Teacher Medal (เหรียญครูอาวุโส), and was bestowed an Honorary Doctorate in Language and Literature (ปริญญาดุษฎีบัณฑิตกิตติมศักดิ์ สาขาภาษาและวรรณคดี) from Chulalongkorn University.
Kamchai died of a blood infection on August 26, 1985, at the age of 79.