As exciting as my trips into Thung Yai accompanying Kamattan Buddhist monks between Washuku and Thong Pha Phum have been...
... there are admittedly more adventurous souls out there, some of whom have traveled a good deal along the same roads and tracks that we have, only on motorbikes.
Here are two photo-rich travelogues posted by guys who travelled along the Thai/Mynmar border going much further than we have, over stretches a truck definitely could not make. Recommended viewing:
Dirtbike trip in 2013: http://teakdoor.com/thailands-travellers-tales/126443-missing-link-riding-sangkhlaburi-umphang-back.html
Dirtbike trip in 2014: http://teakdoor.com/thailands-travellers-tales/140393-eat-sleep-ride-another-jungle-adventure.html