Having lived in Thailand for sometime, I find the best books that teaches us about the Thai language and good Thai dictionaries can be found in the following places:
- Hualampong train station in Bangkok (there are a few bookstore near the waiting area- good Thai language books are available there)
- Some bookstores that also sell English books- you can find good dictionaries for less than 400 baht
- Chiang Mai airport
- Suvarnabhumi airport (the bookshops inside- they also have online bookstore)
Even if you buy from Suvarnabhumi, the price would still be lower than any of the bookstores found in your native country. Not to mention the selection and choices available.
For example in Malaysia, if I were to get from Kinokuniya, Borders or MPH, not only that they cost up to double the price I get, but the variety are so much lesser.
And if you want to buy books or manuals on Thai massage, I found one bookshop at Chiang Mai airport that sells a good manual on Thai massage- it teaches the points, etc. The bookstore is located on your right as you come in from the main entrance- you need to walk further till the right and you would see a bookstore on your left side. Of course, books sold in airport are slightly more expensive but it would be nothing compared to the price you have to pay when that book is to be bought at your home country.
A great free online resource to learn Thai: http://learningthai.com/