If I am not mistaken, thats the back of the same form we made them give us at the stung treng border.. He wasnt going to give anything, and was angling for soem money so we were also hesitant to make a problem, but did in the end.
If its the one we got, its more a customs declaration for bringing valuables in, like an 'anything to declare' form you would associate with carrying in valuables.. Was all he had in his desk so just used that.
Ours didnt get a vehicle stamp like that.. just some scrible by him, the 'declared value' of the bikes and a signature. No one asked for it (even in sihanouk) and it wasnt given in on exit. There appeared no end date or anything firm. As we could have come in without any of this if we didnt literally wake him up sleeping in the shade, and push him to give one, I doubt theres any working time limits in reality.
You do have limitations how long you can take the bike out of Thailand..
If you fail to return the bike at the set period, there are fines.
Read the fine print on the form you sign when at Thai customs.
Of course.. if you don't care about returning the bike here then it is different.. not sure how easy that would be to keep the plates and registration up to date then.
Agree that form is more like a what do you have to declare.. eg.. Expensive Camera as you are a journo.. etc. No need for this form in reality. According to the person at Koh Kong.. when you get to the other provinces.. Their rules kick in and nothing he says or did will help you..