This is a tricky one. There is somewhat of an urban myth that you are allowed to drive on your driver’s license from your home country for 30 days. Or sometimes it’s “you have 30 days upon arrival to get your Thai license”. And indeed, the vast majority of places will rent you a bike and never ask you if you have one, nor tell you it’s a requirement. To them it’s your problem, not theirs. We actually care about our customers as repeat business and word of mouth recommendation are what we thrive on. As such, we want you to know the truth.
We have verified the actual rules via the land transport office and the reality of the situation is, you are legally required to have an international driver’s permit to operate a vehicle in Thailand. We strongly recommend you get an international driving permit just to be fully legal. For most countries they are extremely easy to get; just pay $20 and fill out the form and show your local driver’s license. If you don’t have one and take your chances driving anyway, you will occasionally get a rather insistent officer that wants his 400 baht… especially if you frequently drive around the tourist areas during the day. Forewarned is forearmed.
Furthermore, only certain international licenses are actually considered valid. Only the countries which were part of the 1949 Geneva Convention of Road Traffic, are acceptable. That convention basically set about establishing rules of the road that everyone would supposedly agree too, and what the licenses would look like internationally. This 1949 version replaced the 1926 version. There was another convention in 1968, but most countries seem to feel the 1949 one was good enough and that’s the one they require. Before getting an International Driving Permit for your Thailand trip, be sure you are getting one that has the 1949 endorsement. Over 150 countries issue this version of the IDP, but there are still some that issue the 1926 version, notably Germany, so please be aware of this rule.