I get that flights to Yangon are dead cheap from CNX at the moment (1490 was the price I saw recently) but you're not considering that most who go to Vientiane fly to Udon Thani and bus the difference. Also you can get a VOA for Laos, you need to apply for a Myanmar visa in advance.
Cheapest destination direct without requiring a visa would be Kuala Lumpur. There are cheaper flights to Yangoon but a visa is required to even get on the plane.