How did Burma change sides in World War 2?

Answer 1

No, it did not really change sides. Burma was on the side of the Allies during the Japanese invasion. The Japanese army established a puppet government in the part of Burma that it ocuppied after they invaded. The Allies liberated Burma at the end of the war. The Allies did not treat Burma as an enemy, only those members of the Japanese puppet government.

The Axis powers often setup these puppet governments in countries that they invaded & ocuppied. Japanese had puppet governments in the Philippines, China, etc. The Germans had puppet governments in Poland, Norway, Belgium, Yugoslavia, Greece, etc.