If the recent Armenia Azerbaijan crisis was anything to go by, in mountainous terrain a drone/artillery combination is quite effective but a relatively new combat style on the scene.

>> in mountainous terrain

In mountainous terrain with few trees. Drones, and air power generally, become less effective over a dense canopy. The dry bare mountains of Afghanistan was a paradise for drones. Southeast Asia's jungles and river networks won't be.

US has a solution for this problem neatly packaged in barrels of all colors of the rainbow.

Welcome, Agent Orange... Let's hope we never see a repeat of such madness again.

Yangon surroundings is a plain, with a lot of roads, and agriculture, and it is situated on the coastline.

The same is much with the rest of South Myanmar, where most of country's population, and economy is.

Saigon and Hanoi are on flat coastal plains too, but you don't decisively win a war by only controlling part of the country, and Myanmar's economy is propped up by gas reserves and other resources in the wild northeast. Myanmar's army is less likely to inspire devotion than North Vietnam's, but can easily be propped up by China if it fancies a proxy war. The likely result of conflict would be everybody being a loser.