Will you not have a problem trying to extend the 30 day exemption while you're waiting for your new passport? - Don't you have to send the old passport along?
Worth checking - if so, recommend tourist visa application in Malaysia so that you get 60 days.
They've probably stopped it ahead of Songkran - the Mae Sot border is currently very busy with migrants crossing for Thingyan - around 8,000 people a day.
For those needing to cross at Mae Sot, the afternoon is better - huge queues in the morning.
Imagine they may reinstate the visa run van after the Songkran/Thingyan season.