When i was in Mae Sai i walked to the bridge, got stamped out of Thailand then presented my passport to the Myanmar authorities who relieved me of 500 Baht, kept my passport and issued me with a temporary permit which allowed me to cross onto Myanmar. Your passport is returned to you when you return the temporary permit crossing back to Thailand. Once in Tachilek you are not allowed to stray further than 5 kms from the town. I believe the procedure might change soon, if it hasn't already. Once you enter the Myanmar side you will be greeted by friendly, yes, i say friendly tuk-tuk drivers offering to tour you around the town
Flying in and out of Tachikek can be a bit of a hit and miss deal. Flights in or out are often cancelled, due to instability at the border between the Burmese and Thai. The flights are also seriously delayed a lot of the time. You can also not necessarily rely on the accuracy of directions from the airport staff.
After being detained in Tachilek, disallowed from crossing the border, and having to wait a day to get flights back to Yangon, I was fairly peeved. When a plane landed at the time we were supposed to leave, we assumed it was ours! We were stopped at the doors and told it was NOT our flight - followed up by another staffer asking why we were not getting on our plane!!! I nearly created an international incident by sending a poorly worded fury SMS to my sister, whose husband, a policeman interpreted as we were being forcibly detained in Myanmar. He contemplated contacting the Australian Federal Police.
Thankfully, our flight was only 40 minutes late leaving, and 90 minutes late landing in Yangon.
So, if you happen to fly in our out of this destination, bring a book and a leisurely timetable, and expect to be late!
We laughted at the tourists in the photograph rushing to the door to get on the plane. However, we did understand the "get me out of here" sentiment, by that stage.
Scooter car is the most economical way to take a look in Tachilek.
It has cover to avoid sunshine and has good view to see the border village.