by the time that said Thai Traffic Law 42 was written, a "temporary visitor" was allowed no longer than 30+30 days per ONE entry inside the country. There weren't any 1-year visa available in these days 😉
"citation needed" . . . . nowhere in your text Thailand gets especially mentioned. Also in the Thai traffic law 42 nowhere is mentioned that a license is valid for one year
he means the new DTV, which gets you stamped in for 180 days. . . . . . . . . Or maybe he meant the multi entry 6-months tourist visa. Which actually only gets you stamped in for 60 days, on every entry during a 6-month visa validity
it should be noted that although IDL and IDP’s are valid for 1 year after arrival in Thailand, after 3 months most comprehensive insurance policies are made void if you are still driving on a foreign licence. This actually voids the use of an IDP for longer than 90 days
YOU ARE WRONG it doesn't matter if you got the 1968 or the 1949 IDP: in Thailand you can use that IDP for 90 days, AFTER this you either need a Thai DL or you need to exit Thailand and re-enter, to start another 90 days