Myanmar Visa Service

Visa requirements to visit Myanmar change on a regular basis so travelers should check with the nearest Myanmar Diplomatic Commissions abroad before making travel plans.
Myanmar Government declares that "all nationalities" must obtain visas before travel to the country. Some additional restrictions, requirements or conditions may be applied to applications - reports have included a need for a detailed itinerary, a detailed job history, etc. be prepared for some unusual questions (either on the forms, or from the Consulate staff) when applying for your visa. Though not explicitly stated, it has been reported that the authorities only allow one trip to the country every 6 months.

Tourist Visa is valid for (3) months from the date of issue. The duration of your stay in Myanmar is 28 days from the date of arrival. It is not extendable. Successful applicants will also be issued an "Arrival form", which will be stapled into your passport and must be presented on arrival in Myanmar, along with your passport containing the visa sticker. Ensure that the visa sticker, and arrival form have both been signed by the immigration officer before leaving the Embassy. Note that you will still have to fill in the usual customs and immigration forms on your flight into the country.
If you can not find a embassy near you, you can still apply for an approval letter. No trip to embassy is required. Simply upload your photo and a scanned copy of your passport to get the approval letter. The Ministry of Hotels and Tourism has made a special arrangement with Ministry of Foreign Affairs to allow the approval letter to be applied online. The process may take up to two weeks. You must enter Myanmar through international airports and not through the border. Visa sticker will be stamped on your passport on arrival.

(From wikitravel.org)