You Do Need power plug adapter while traveling from Mongolia to Myanmar (Burma).

Here is Why You Need An Adapter

The outlet and plug type used in Myanmar (Burma) are A, C, D, G and I and in Mongolia are C and E. This is how they look like.

Mongolia

In Mongolia, outlets of type C and E are in use.

Type C

Type E

Myanmar (Burma)

In Myanmar (Burma), outlets of type A, C, D, G and I are in use.

Type A

Type C

Type D

Type G

Type I