There's a lot of conflicting information here. You need to check the Thai consulate in Cambodia and see what their specific requirements are. If they do allow evisas you can certainly apply for one beforehand just as long as you have a ticket showing you will be going to Thailand from that country, but keep in mind that the visa has to be used by a certain date.
I think it depends on your airline... mine always checks to see if I'm leaving before the tourist visa expires. I just rebook the flight once I'm in thailand
Also when traveling to Krabi I recommend you store your stuff in Phuket since they're so close to each other. You can pack light and go for a few days.
Thai drivers are notorious for excessive speeding, tailgating, and not following traffic rules...plus you have motorbikes swarming around all over the place and they always have the right of way (since youre in a larger vehicle and you're a foreigner). I'm used to it now, but it still stresses me out sometimes when I drive. I honestly don't see any reason for a tourist to ever rent a car in Thailand since taxi and private car services are so cheap (compared to western countries).
Honestly you should be fine and tourists do it all the time (just get the larger SUV option for grab) but I do agree there's really no need to pack a lot of things. As for driving, I've been living/driving in thailand for 6 years now and I really wouldn't recommend it. 😕
Depending on your local immigration office, you can probably go within the last 30 days to get a 30 day extension of your 60 day tourist visa. Then take a trip to a neighboring country (heck stay a few days) and upon your return to Thailand you will get a 30 day visa exemption assuming your passport is from one of the countries on the exemption list.
I stayed in Thailand around 20 months (visa exempt and Covid extensions)....went home to the US for about 4 months and came back on a tourist visa and had no issues getting back in. I'm currently on my first Covid extension yet again.