You can also apply for a tourist visa which is 60 days initially that can extend another 30 days. Visa exempt gives you 45 plus a 30 day extension. Both these options can be changed to a different visa in Thailand if you wish to stay longer.
the actual international dl will have an expiry date, usually a year or longer. However in Thailand if you drive you ‘have’ to get a Thai DL within 3 months.