How much would one expect to make teaching english in Bangkok - how much is the training?

You need a TEFL certificate and necessary paperwork from Thai authorities for correct visa. I doubt if you can expect to get a job at school for only 3-4 months you would have to sign at least a year contract. Expect pay between 17-20000 Baht a month. Does not sound a lot but you can get basic accommodation for as little as 5000 baht a month . Teaching in Thailand is to help the Thai's learn English not a way of making money and living the good life. There are courses on the net for under $200 for the TEFL course but cost's depend on what Country you are from. I have been looking to do Volunteer work in Thailand but yet to find a site that you do not to contribute to. Hopefully some one who know's more than me will find out about paid Voluntary work for you. Good Luck

Thailand is not about volunteering, it is about ripping off tourists like yourself. Forget volunteering in Thailand

Try ajarn.com (see the link) for lots of answers to this question and stories how some teachers actually make a decent living (most don't).

That has dried up in the last few years, mostly because of high unemployment in the states. Hundreds of people fly in thinking they can find a job. The jobs are there, but there is a lot of competition. The schools can pick and choose. Another factor is that the overall level of English is improving. The schools can hire a local university graduate who speaks well enough to teach beginners. The locals work for 500 a month, don't need a permit, and speak fluent Thai. Also, many schools have been taken over by US ngos so that they can shovel out religious propaganda.