Myanmar Constitution allows voting rights for overseas voters. In 2015, Burma Campaign UK estimates that the number of people who were disenfranchised or unable to vote is around 10 million people, or 20 percent of the population, of which 5 million migrant workers living abroad, 200,000 Rohinya refugees in Bangladesh, 109,000 in refugee camps in Thailand,
The number of registered overseas voters in 2015 is rather low. The last census showed that Myanmar has over two million people living overseas, less than 2% will be voting at Embassies and Consulates outside of the country. Many of those working in neighbouring countries are only on temporary passports, and holders of these documents were not allowed to register to vote at embassies.
Most of these are Myanmar skilled workers in Singapore where 20,000 out of 150,000 have been registered to vote. In Thailand, only 300 were registered even though there are more than a million migrant workers. In Malaysia, 500 out of its 300,000 migrants would get to cast a ballot.
The main challenges for registration as an overseas voters were bureaucracy, uncertainty over the deadline to register, a lack of documentation required, and embassies not being proactive in informing people about the registration, as reasons for low registration. Chaos and mistakes with voting forms for the few who have registered at embassies abroad has been widely reported. In a random sample of people attempting to vote at the Burmese Embassy in London, 30 percent reported they had been unable to do so.
Source
Chat Win, Making Myanmar’s overseas vote count, New Mandala, Oct 19, 2016, http://www.newmandala.org/making-myanmars-overseas-vote-count/.
DVB, For Myanmar Nationals Living Abroad, Overseas Voting Sucks, Coconuts Yangon, Oct 20, 2015, http://yangon.coconuts.co/2015/10/20/myanmar-nationals-living-abroad-overseas-voting-sucks.