Its about 680 kilometres between the two but isn’t that difficult to transit between them. The quickest way is undoubtedly via air (1.5 hours), with loads of carriers – Air Asia, Thai Smile, Thai Airways etc – offering convenient and affordable flights.
You can also take the train but this takes between 12 and 15 hours and is not known for it’s comfort! Night trains make the journey at bit more palatable as you can book a sleeper berth.
There are also a number of busses, from cheap local options to VIP minibuses, all taking approx. 12 hours between the two points.