ATTENTION MEMBERS (Especially ones in the north west)
The land border at Mae Sai - Tachiliek has stopped allowing people to bounce out and back by buying a day pass (500baht/$10USD) and now require a person to hold a valid VISA to Myanmar BEFORE you can stamp out and back at that border.
This is the link to BUY an eVISA for Myanmar.
[members only]/
UNLESS you are from a country that gets visa free entry to Myanmar you CANNOT bounce at Mae Sai -Tachiliek without getting a visa to Myanmar before hand.
Thanx go to Charlie Brennan for this information. He was the FIRST foreigner turned away when they started the policy :O
TLDR : Answer Summary
The Mae Sai - Tachiliek border crossing now requires travelers to hold a valid visa for Myanmar before crossing; day passes are no longer accepted. An e-Visa can be purchased online, unless the traveler is from a country eligible for visa-free entry. Users have reported mixed experiences at the border, emphasizing the need for advance planning and verification of current entry rules.