Visas are not required for passport holders from Brunei, Cambodia, Indonesia, Laos, Philippines, Thailand and Vietnam for visits up to 14 days.
Tourist visas for Myanmar, with a 28 day validity, are available from any Myanmar Embassy or Consulate worldwide. These visas cannot be extended.
It is possible to get a visa on arrival at Yangon airport as long as you have clearance from a Myanmar tourism company or an evisa. It may be cheaper to get the visa from an embassy. The evisa is available for about 100 countries and is only available for entry at the airport.
We have had multiple reports from people that you can get a visa on arrival at Yangon airport without any pre-clearance. The airline may not let you board the plane to do this.
The borders with Thailand are open, you will need a visa in advance (not an evisa) if you intend to arrive from Thailand. There are options for a a visa on arrival but they are limited to a few days and to a small area near the border crossing.
The borders between India and China are somewhat open. You can obtain a permit by applying in advance at a consulate or embassy. It costs around US$250 and takes at least a week to organise. Crossing to/from India is possible by arranging a permit in advance in Yangon.
Visa requirements change regularly and differ between consulates. In general the embassy iin Bangkok is quicker and easier than most.