So, you have decided to ignore the advice given on my page with language tips for first time visitors to Thailand. Otherwise you would not have arrived on this page.
On this page I give some advice where and how you can learn the Thai language. Please realize that this will be a process of years, but of course it will be very rewarding if you succeed. Only a few Westerners do!
Learning to read the Thai language
The first piece of advice I have to give you, is that you will never, ever learn even the basics of this complex language properly, if you do not start by learning the Thai alphabet, and the tone rules. Only the Thai alphabet will show you the tones correctly. There is no alternative for this. So you should first find a site where they teach you the alphabet. And after that you should ignore any transliterations into English, which you will (often) come across. They can never replace a thorough knowledge of the Thai alphabet.
The following sites let you start with the Thai alphabet:
A good site is set up by the Northern Illinois University (NIU).
Go to their Thailand home page and click on the left hand panel for the main menu. On top you see some sources to learn the Thai alphabet. The Thailand home page is also under the logo below.
If you want to give your Thai learning a flying start, you could also start with Manee book one (see below). Book one in their version also starts with the Thai alphabet.
After you have mastered the Thai alphabet, you are ready to learn to read.
You may believe me that I have tried many different sites and books to learn elementary Thai reading. I started with a small book called "Easy Thai", but believe me, there is no such thing as easy Thai, so that book will not help you, apart from learning you to recognize a few Thai characters and learning to count (which, by the way, is essential when walking over Thai markets). Furthermore this small book teaches you that there are rice farmers in Lamphun. Nice to know, but not really useful in Thai daily life! So forget about this book and similar books. They are useless for learning Thai.
Many years of trial and error have given me the insight that there is but one good source to learn to read Thai: Manee (sometimes also called Maanee, Manii, or variations of these spellings). This is the ultimate source!
The Manee books (in total twelve) have been used for many years as a tool to teach Thai school children to learn to read their own language in elementary schools. My strong belief is, that if Thai school children, who can not yet read, can learn it from these books, a Western adult certainly should be able to learn the trick from the same material.
So, where can these "miracle books" (because miracle books they are) be found?
A source for Manee (and here you will find books one and two) is the Saesite Thailand site, with text and MP3. Manee is called Manii
here. The first two Manii books (40 lessons) give you a great start with the Thai language.
Recently (2012) a Thai lady called Mia Rongsiaw, who is a teacher of the Thai language, (you can also take Skype lessons with her!) started the project to make all twelve Manee books, with transliterations, complete translations and sound files accessible for foreigners who want to learn Thai. Her site is called Learn 2 Speak Thai. Go to her Manee pages by clicking the Manee book below. She does a great job and we wish her all possible success and many visitors on her site!
And last but not least, all twelve Manee books in their original form can be downloaded, legally, as PDF files from Dropbox. (They are all completely in Thai, so you could better start learning from Mia's site).
Click on the 6 links at the bottom. Each link will lead you to two Manee books.
See an interview by Mia Rongsiaw with the author of the Manee books.
Learning to speak the Thai language
Probably the most thorough course to learn to speak Thai is the FSI (Foreign Service Institute) course. This is a course, originally written for American diplomats and it is of a high quality.
It has been commercially available for many years for quite some money, but now it is in the public domain. Find the complete course (all books and all sound files on the FSI pages.
The course in its original form used a transcription of the Thai alphabet. However, a group of volunteers has re-written the course in the Thai alphabet. This must have been a tough job!
Find this excellent piece of work (with the main sound files embedded) on the Thai language wiki. Learn the alphabet and follow the course there!
When you have finished the FSI course, you need further reading lessons. You can find them from an excellent Thai Reader (with sound files!). This reader was also written for FSI. It can be found on this page from Siamwest.
But my warning was and is: The Thai language is a very difficult language for westerners to learn! And the FSI reader is not easy. Better first finish your Manee books!
Links to other Thai learning Sources
All the sites mentioned above have many learning materials. Use them one by one, and do not start several courses at one time! This will not work and only will confuse you.
The most extensive source to everything related to learning Thai is doubtless Women Learning Thai. It is a blog that discovers new sources or people related to learning Thai almost every day. Subscribe to their RSS feed and you stay up-to-date.
I found the reading exercises with sound files on Siamwest for intermediate readers very useful.
And if all this is not enough try Google with the searchterm "Learning Thai".