Myawaddy (also sometimes spelt Myawaddi, Myawadi or Myawady) is a border town in Myanmar. Access for foreigners is currently only possible from Mae Sot in Tak Province, Thailand, though this is set to change in a few years time.
At some point in the next few years (possibly late 2009) this will become a full international border crossing as part of the Asian Highway Network route AH1 which will connect Tokyo in Japan with the border between Turkey and Bulgaria. At that time the Mae Sot - Myawaddy border crossing will probably become the main overland entry point for foreign travellers wishing to get from Bangkok to Yangon (and vice-versa) overland.
Currently however foreigners may only enter on foot, are not allowed to travel further overland into Myanmar from Myawaddy, and are not permitted to stay in Myawaddy overnight, hence they must head back to Mae Sot before the border closes at 18:00.
Despite these restrictions, the Myawaddy - Mae Sot border crossing is a moderately popular destination for tourists and expats in Thailand who want to make a "visa run" (i.e. get a new Thai entry permit stamp by making a short visit to another country).
The time in Myawaddy is 30 minutes earlier than in Mae Sot, and the traffic (mostly) drives on the right.