Un saldo medio es lo segundo, no tiene que ser un mínimo cada mes sino la media en los últimos seis meses. Es un certificado muy común que te lo dan al instante en tu banco.
I think is clear, they ask a bank statment showing different amount of money if you work for somebody, by yourself, retirement... Anyway you can apply the easiest visa, a SETV (Single Entry Tourist Visa) and after 90 days (60 days stamp plus 30 days extension) you can do a visa run to a neighbour country for a new SETV.
Yep, but the thing isn't "no visa, no flying", the airlines ask for a ticket out of Thailand before 30 days if you wanna fly without visa. But, even you don't use, is enough any cheap flght, bus or train ticket. Often cheaper than a visa If there is not any thai consulate in your home town and you have to travel to another city.