The new Thai licence (bilingual Thai-English) is fine to use in Laos although apparently it should be the 5-year type, not 1-year type. Even so, on the one occasion I got stopped by the police near Pakse (I happened to be driving a Lao pickup truck towards Thailand) my 1-year Thai licence seemed to be good enough, besides the Lao cops probably wouldn't know the difference anyway. Vietnam and Cambodia are another matter. Although Vietnam now reportedly accepts international driver's permits issued by 72 countries, not sure if Thailand is one of them, despite all the rhetoric we hear from the Thai Land Transport Department. But I wouldn't trust much of what they have to say: they claim that a purple international transport permit can be used for Laos, Myanmar, Cambodia, Vietnam and southern China, when in fact only Laos recognizes it so far. China and Vietnam don't allow Thai vehicles in at all, unless you go on a tour, while Myanmar is the same except for short trips near the border, which only requires the vehicle's registration. Cambodia only allows in Thai vehicles at some crossings and even then, they aren't supposed to leave the border province and the registration is all that's needed. Also, Cambodia doesn't recognize Thai driver's licences, though they may not care if you are only driving a Thai registered vehicle near the border.
The Thai government has repeatedly also claimed that all 10 ASEAN countries accept Thai driver's licences. I disagree. The only ones that will, apart from Laos are Malaysia and Singapore. These three countries also happen to be the only 3 countries Thai vehicles can enter without restrictions. All other countries have either travel restrictions (Cambodia and Myanmar) or require massive amounts of red tape and expense to be allowed to enter at all (for example, China and Vietnam).