as with many places, anything not secured or left, will sprout legs. Most of Thailand is rural and very poor. Hire a Thai driver or use public transport. In an accident, and there are many, even if you were clearly not at fault, being the farang, you are rich and will pay. The laws are generally against you. Money generally solves issues, but let a Thai person negotiate since you will not be sensitive to the cultural nuances and you are not fluent in Thai . Never make physical contact with a Thai person without clear invitation. Thai are generally happy to be photographed, particularly if you ask first. Some areas will be marked no photography, respect it. No shoes in temples.
Dress and behave conservatively. Most Thai adults do not wear shorts or tank tops. Learn some basic Thai. There are free websites to learn basic language and customs.