Same-sex relations are criminalised under the nation's colonial penal code, and although it is not strictly enforced, activists say the law is still used by authorities to discriminate and extort.
The celebrations are part of the International Day against Homophobia and Trans-phobia and will take place in four cities across Myanmar, according to Aung Myo Min of the Human Rights Education Institute of Burma.
There will not be a parade, unlike at gay pride events in more liberal countries.
Instead, music, plays, documentaries and talks by authors will mark the occasion in Yangon, Mandalay, Kyaukpadaung and Monywa, Aung Myo Min said, adding that the events have been officially sanctioned.
"In the past a crowd of people at this kind of event would be assumed to be against the government -- taking part in something like a protest," he said.
"Now LGBT (lesbian, gay, bi-sexual and transgender) society has courage... and they dare to reveal their sexual orientation."
Totalitarian politics along with conservative religious and social values have conspired to encourage many gay people to stay in the closet in Myanmar, formerly known as Burma.
Attitudes contrast markedly from neighbouring Thailand, where a lively gay and transsexual scene is a largely accepted part of society, which -- like Myanmar -- is mainly Buddhist.
But dramatic political change since the reformist government of President Thein Sein came to power last year is rippling out to wider society.
Calling on the government to repeal laws criminalising gay sex, Aung Myo Min said taking part in an international event would empower Myanmar's gay population.
"They will have more courage to reveal their sexuality," he said.
"If we don't discriminate against them and respect that diversity, the world will be more beautiful than now."
The past taboo on homosexuality in Myanmar has restricted awareness of sexual health among gays.
In some areas, including Yangon and Mandalay, as many as 29 percent of men having sex with men are HIV positive, according to a 2010 report by the Joint United Nations Programme on HIV/AIDS.