Some successful punters have made entire businesses that sell goods on ebay like the silver jewelry man in Bangkok who now has 30 employees and sells from ebay and expanded into his own website.
Many a foreigner either corrupt young girls who aren't in the business or find someone who already is and then get customers through the Internet as well as bars.
If you can find a young good looking Thai girl and somehow convince her to do this for you, you can make a lot of money.
Be warned though, this is illegal and the chance of your Thai girlfriend contracting a disease or simply moving away with one of the customers is very high.
To keep her in line you'll need to be prepared to beat her into submission.
Teaching English in Thailand is a decent and fair way to make money in Thailand, it does have it's pitfalls though.
Most people who come to Thailand see Teaching English as an easy way to make money and more often than not are not trained to do so.Finding the right product to sell though will take some time to master.Many a backpacker has come here and sold fake items on ebay to raise some money, but in the end selling pirated goods can't last long you'll only get yourself kicked off ebay.If you open a bar that caters to foreigners and tourists you are at the whim of the current political climate and whether tourists come or not, 4 months of the year will be extremely quiet and likely to lose money 4 months running.Many people are selling Thai wares on Ebay these days.The perks however are you get 4 months vacation per year while still getting paid, though on a meager teachers salary there's not much you can do in that period of time.