http://wikitravel.org/en/Discount_airlines_in_Asia

This is another good site for you. Lists all discount airlines from Hong Kong and in Cambodia.

I don't think I would risk a 55 minutes connection domestic to international anywhere, it is such a risk especialy if you then have more connections.

Overnight near BKK is better than it was

http://www.asiaoz.com/bangkok_airport_hotels.html

Shows which places offer free airport transfer shuttles for BKK, and there is a reasonable choice now.