I volunteered with Open Mind projects for about 4 months and I had sooo much fun! I taught English in the volunteer center in Nong Khai for a month and in a village in Phuket for the rest of my stay. In Nong Khai i received a 3-day intensive cultural and language training which really helped in the communication with the locals and the students as well as behaving respectfully towards the locals, so if you are thinking about volunteering for this organisation, I absolutely recommend it. It a bit tiring, because for 3 days you learn so many things, but it is also very helpful. The accommodation in the training center is not great, but it is comfortable, even though it can get a bit warm at times, despite the fans. Also, the stuff of the organisation are very friendly and helpful.
While I was staying in Phuket I lived with a host family. At first I was feeling a bit nervous about doing that, as it was my fist time volunteering abroad etc. but they people from open minds talked me into it and i never regretted it.The family was very welcoming and polite and I had my own room with 2 fans! The assisted me in every way possible and they were just amazing :D In Phuket I taught in a school and helped in the promotion of the local activities for tourism purposes.
Teaching at schools was a wonderful experience and the children give you so much love and most of them are really interested to learn. Yet, it is school so there are always troubles with some. Also, Open Mind projects encourages the "learning by doing" teaching method which I found very beneficial for the students, as it helped them memorize things better! So, you have to be creative and come up with games to teach them things, which can mean as much fun for you as for them.
Also, Thailand is so very cheap! Both Nong khai and mai-khao, the village i stayed at in phuket, were very cheap. You can have an hour for massage for less than 10 euros! An extra bonus to the very low fees of the open mind projects, which are very reasonable.