I've had pretty good experiences with Bon Voyage Travel in Makati. I can't seem to find their phone number or location at the moment. I'll let you know if I can dig it up when I get home.

I'm not sure what fares are like at the moment, but in general, I've also found that ex-MNL fares are best booked locally. I've seen BKK vacation packages for <$300 ex-MNL, including 3 nights in a hotel, but that was about a year ago. The most recent quote I got from a travel agent in Manila was for MNL-BKK-HKT r/t on Thai for $800 in business class. Seemed a bit steep and I didn't end up booking it, but it was still less than what Expedia et al were showing at the time!

Also, as a foreigner, you should be exempt from the "Travel Tax" that the PI government imposes on its citizens, but you may need to fax the travel agency a copy of your passport. Good luck!