Cambodia land or air is just fine. It all depends how many stamps you have in your passport. If it will be your first or second border bounce you will not have a problem with either.
However DO NOT GO to the Poipet Border.
The other 2 good land borders are in a remote area and I would recomend you get a visa run service to make things easier. If you are new here it will be harder to find a minivan that goes there.
I would not fly to Cambodia (Phnom Penn). The city sucks.
If you want to do a border run by air I would fly to Da Nang (Vietnam) and go visit Hoi An.
If you are looking just to spend the least money as possible I would pick the land border with an agent. Go and come same day.
I also have the 90-day bilateral agreement and extension in Thailand is only 7 days.
Better to exit and come back so you get anoher 90 days
if you are an American you can get the company under your name BUT for the work permit there is no way around it. 4 employees for the WP or 2 if married to a Thai.
It is a shame the government doesn't give the right to work for foreigners married to Thais like in most countries. Very very unfair treatment.
As a start up I would just put the biz under the wife's name, if things take off you can add your name later or do the amenity.
If you are investing a lot of money in the start up I would go the proper way. If you are not investing a lot I would go the easier way.
at this point if I were you I would avoid airports.
Second I exit and go to my embassy to get a new passport. Yes it links to your old passport but when you have a line of hundreds of people the immigration officer only looks at the stamps in your passport not your history. They will look at your history if you get called to the side.
I would contact the visa run company that leaves from OnNut Tesco Lotus parking lot. They will be able to tell you if they can do a visa run safely.
I think it is impossible to give you any clear answer because we don't know your lifestyles, age, standards of living and city where you plan to live. My health insurance covers up to 500k usd w a higher deductible, I am healthy in my mid 40s so my insurance is only in cases of emergency cost 20k baht a year.
Cost of living in Bkk is much higher than other parts of the country. Do u plan on living in bkk or another province?
A descent 3 bedrooms condo is about 40k baht in the city in a good area.
Electricity if u can live without AC is around 1000 baht. With AC running 2500 baht and up.
I chose to live in the center of the city so I don't need a car. Traffic is truly awful.