It is all in the game, to avoid the stress and hassle, get the correct visa for your long term stay in Thailand, even when you do not like the set requirements. After all, it is YOU who want to live in the land of smiles.
With a Non Imm O visa you only get 90 days of stay inside the Kingdom and have to leave to obain a new 90 day period of the visa is multiple entry OR apply for a new visa.
BUT if you got this visa, entered Thailand and visited the Immigration Office to get a new big stamp with the text:
"Extension of Stay permitted up to xx/xx/xx" which is valid for 1 year, you have to report that you are 90 days inside the Kingdom.
Please look in your passport and tell us which one you have OR just show us a picture without any personal details to help you out correctly.
IF it is the big stamp Extension of Stay, you can use this on line system
You can buy a Re-Entry Permit but be aware that does not give you extra days, on return you will get the same Admitted until day as you got on your first entry
Yes, a Single Entry visa means you can use this once, on entry the visa get the stamp used and becomes invalid. You get a maximum stay of 60 days and you can leave anyday during those 60 days.
On return you might want to use the 30 day Visa Exempt Entry or buy a new tourist visa at the Thai consulate before travel.
Alternative is the 6 months valid Multiple Entry Tourist Visa, which will give 60 days of stay on each entry during the 6 months validity of the visa.