Traveling to Myanmar over land through Mae Sai (Thailand) border crossing is now possible. The only way to get into Myanmar before was to fly into Yangon, and then take it from there.  The new border crossing has been officialy opened since August 28, 2013.  

Three month visas can be obtained on the same day for extra payment or the next day at the Myanmar Embassy in Bangkok. You Can cross over thru Mae Sai (Thailand) to Tachileik (Myanmar) and after that, its possible to go on the bus, but trains are also available if one travels from Tachileik to another nearby town on the bus.

Hope this is helpful to many who want to see the golden land, overland!