I'm your everyday Caucasian American. I studied at ABAC for a year in 2002. I was paying around $1,000 per semester. Back then, the exchange rate was $1 = 42 Baht.
Today, the exchange rate is about $1 = 34 Baht. The average tuition for Business/Economic majors per semester at ABAC is 50,000 Baht. So, you should plan on paying around $1,500 in tuition per semester. Of course, you'll also need to pay some silly fees when you first join--matriculation fees, ID fees, and other stuff.
You can ask me about ABAC if you want. And I'd tell you the school lacks every ounce of professionalism you would normally expect from a University. If you do go to ABAC, find the international student office as soon as you get there. Don't even bother talking to the registrar.
I would highly recommend looking into other international programs at Chulalongkorn University, Thammasat University, Mahidol University, or even Bangkok University before deciding on ABAC.
By the way, the guy who posted above me (Sr) is wrong. Thailand likes and needs foreign investment. The SOT does license foreign stock brokers to help bring in foreign money. You may not be able to open your own brokerage house without a Thai partner, but you can work as a broker. I know at least 2 foreign brokers there. Though I have not verified this, I've heard that SOT may even offer the licensing exams in English now. You may also work as a Stock Broker selling stocks from your own country to Thai people.