If I, as a resident of Bangkok, have to fly to a nearby country outside of Thailand, I will probably do so from there Don Mueng Airport in the north of Bangkok, from which the flight prices (at least in my experience) are significantly lower than from Suwannaphum ( "Suvarnabhumi");
The differences can reach thousands of baht.
But I wonder if there could be an airport outside of Bangkok where airfares to nearby countries (Laos, Cambodia, Vietnam, Myanmar) are significantly lower than in Bangkok.
For example, if you go somewhere outside Bangkok with a 3-hour bus in 150-200 baht, you can save 1500-2000 baht with a Don Mueng plane ticket.
If you drive outside of Bangkok (within a 3 hour drive, probably by bus), can flights to neighboring countries be cheaper than Don Mueng?