Can I return to Thailand on a 30-day visa exempt stamp after my family visa expires, and what are my options for obtaining a Non-O multiple entry visa?

You're definitely NOT going to be able to fly in and out endlessly on 30 day visa exempt entry stamps. Sooner rather than later you're going to get pulled aside, questioned, told to get the right visa OR get denied entry. :O

By "family visa" do you mean one based on marriage or one based on supporting half thai children?

The reason I ask is IF you have one based on marriage, just go to either the thai consulate in Savannakhet Lao or HCMC Vietnam and get a year-long, multi-entry Non-O visa based on marriage with no proof of funds and only minimal documentation. It'd be good for unlimited entries of 90 days each for the year the visa is good for.

It's a thought anyway..

I would go to your immigration office and show them that you will be out of the country when your current extension expires and won't be back until after it is expired.

They can make an allowance so you can get an extension before the 45-30 days early IF they want to

"Will I be able to return on a 30 day visa exempt stamp?"

Maybe, what's your nationality? See 120-2-9.pdf for the list.

"If yes, how many visa exempt entries before I get pulled?"

You have two entries each calendar year by land, and "unlimited" by air. "Unlimited" is defined by the immigration officer on duty. You can not live here on back-to-back visa exempts.

"where is the best / easiest place to get a Non O multiple entry visa?"

All of them should be easy, depending on your nationality and requirements. Savannakhet and HCMC are the easiest, and don't require proof of funds.

" have been pulled by immigration once 4 years ago and told to get a visa, which I did but will this be recorded somewhere and cause a problem?"

If it was just a simple talking to by the immigration officer, then no, it cause any problems and wasn't logged in any database. If there is some stamp on your passport, then it may cause problems in the future.

The 30 day stamp should be no problem. Are you married? It's easy to get a multiple entry non-o in Savannakhet Laos based on marriage. No need to show financials either.