English by Example: A Dictionary of English Collocations with Thai Translations by Wong Wattanaphichet.
This dictionary is at the top of the list because it is the ONLY English to Thai dictionary that has absolutely zero errors in English grammar! The author of this great work had emmigrated to Thailand from southern China back in 1948. He subsequently learned the Thai language while working for a local newspaper. His command of the English language is very impressive although he is quite modest when he admits in his introduction to this book that he is still learning English. All ESL teachers should strongly recommend this book to thier intermediate to advanced students.
Dictionary in Action – English-Thai by Example Usage (3 in 1)
This is the lowest price English to Thai dictionary that has a comprehensive content with example sentences. The only downside to this edition is that the printing quality is quite low and the typeface is very small. Also, the English sentence examples have numerous grammar errors. However, I am quite sure that the Thai sentences are grammatically perfect; so if you are a student of the Thai language, you will find this dictionary quite useful. If you are a native Thai speaker who is studying English then you had better use this dictionary with caution and ask your English teacher to correct the errant English sentences for you. All things considered, this dictionary is a worthy addition to any learner’s library of language-learning tools.
Oxford River Books English to Thai Dictionary by Oxford-River Books
This is by far the most comprehensive English to Thai dictionary published to date. It is primarily for professional translators as it has just about every obscure English word listed therein. There are special sections for English speakers who are studying Thai language as well. Quite impressive in its scope of listings. Downsides are: 1) very small typeface. In many cases a magnifier is needed to accurately read the Thai script. 2) The book itself if quite bulky at over 1200 pages! However, if you are really serious about studying English or Thai, this is it!
Windows into Southern Thailand 