From the east coast, Thai Intl Airways would be best - shouldn't cost more than $1,000 or $1,100 (just for the international segments) if you leave before Memorial Day but its a bit more expensive in the summer.
A lot of Asian airlines sell tickets in bulk to travel agents and give them a "buy 8, get one free" or "buy 10, get one free" type of deal. The agents then turn around and sell you tickets at 10% below what Thai Airways would charge you. Your best bet would be to find a travel agent that is not a "free-agent" but actually an agent of Thai International Airways.