Traveling Thailand has become a nuisance for overlanders with 3rd country registered vehicles. You have to obtain a permit by DLT, Thai transportation department, and to employ an agency. You need a Thai driver license and you must hire an accredited agency and a guide plus vehicle escorting you 7 days/24 hours, expensive.
Camping cars, i.e., cars with sleeping accomodation are not allowed at all neither are trucks and buses above 3,5 tons gross weight. Some overlanders try to cross any border between Thailand and Laos, Cambodia, Malaysia or Myanmar without permits being successful with bribes of some 100 US$ now and then.
Special permit was neglected by Thai DLT although truck-the-world had started long before those regulations were implemented. After lenghty discussions with Major Officials, inustrial companies plus Thai DLT and more than 10 shipping agencies and overland carriers we finally decided to neglect trying any Thai border without permit.
A way out seemed shipping from Sihanoukville to Kula Lumpur. That was not successful either because our truck does not fit into standard containers and carriers we contacted do not provide 40 feet open racks. Same for overland carriers through Thailand on a big truck, no offers at all.
Consequently we skipped Thailand from our truck-the-world tour. Funny enough that Thai visa may be obtained upon arrival for 30 US$, valid for 30 days…