You cannot drive legally with your UK drivers license. The international drivers permit allows you to drive in a country which has reciprocal agreements. But this is only meant for you to drive for a short period of time as if you were on holidays. Once the office opens take with you your UK drivers license, Certificate of Residency and Medical Certificate which you can get at most clinics for 200 BHT. Go Early
Steve I now that but when you want the simplest way it is with a Visa company. Especially if you don’t meet the requirements on arrival for first time. In two weeks you have your retirement visa for one year and the following year you will have all your ducks in a row