OneZero...
1. Travel within the Tachileik economic zone (the Town and the areas surrounding it, including the resorts, golf courses, casinos, and night clubs to the East of the downtown) was previously permitted on a day pass (when those were available years ago) or a mini-Visa that was obtained from the Myanmar Immigration police at the border. Overnight stays at hotels in the zone were permitted. Travel outside the zone required a Myanmar Visa and hired transport (including a guide).
I don't know if this will be the case now as I haven't been there in 3 years since before the border closed, but I assume those requirements will not have changed. The Myanmar consulate in CM should be able to provide that information.