Andy,
What you want cant be done, though its certainly been tried. And, the Long Term Social Visit Pass sounds so inviting, doesnt it? An oasis in the desert! An end-all to problems! But in fact, its an ugly thing thats really the opposite. It reminds me of a prisoner in jail being told he is going to spend a week in the Rose Garden, or going on a Summer Retreat, and the reality is solitary confinement, full of electrically-charged barbed wire and no food.
To answer you, yes its possible you could leave to Thailand for a weekend on a visa turnaround, only to have trouble coming back in. Actually, if there was trouble, they would most likely let you in but only for 3-5 days on a pass that forces you to go straight to the Enforcement Office to plead your case and if you fail to convince them, you will be quickly packing your bags. There have been extremely few cases of someone being barred from entry, or even detained at the border, but it has happened. That said.....let me think....a year is three times the 90-day pass... I think you're good. Its a chance i'd take.
Also....be warned about a trap thats far too easy to be mentally tricked about. You come on a 90-day pass and in the middle of that, four weeks in, you take an overnight trip to Singapore, just to see it and you come straight back. Your brain thinks you are still on your 90-day pass, it was just a little side trip, and nobody was watching or cared anyway. NO, you just blew off and wasted the remaining 60 days of that visa and you start all over. Now your year has been cut by two months, just so that you could finally taste a Singapore Sling. You can rightly claim you had the worlds most expensive drink!
The government has myriad types of visas at their disposal but its doubtful they would help your case unless you are a diplomat. They have a Professional Pass, under which you come for six months to check out the country for potential business expansion, and I think that could be re-newed. They also have Medical Tourism passes but you have to be doing a medical procedure. They have Student Passes, you could enroll in school, get the pass and never attend. That might actually be an option.
I certainly understand you and I too have been in that space of wanting to park myself somewhere for a year and chill out and on the belief I can simply GO. But something must slap our faces to awakeness to say, youre mad! whats wrong with you! wake up! If this were only a few years ago it would be easier to answer you. Today, its just getting tougher all the time, and expats are scurrying to and fro trying to figure out anything helpful.
If I were you....hmm..i would just come. You have ample time, you get at least a few turnarounds without problems and who knows, you might 1) hate the place and prematurely run away screaming in madness 2) figure out a way to stay longer, like a Student Pass. 3) plain be lucky and slip through three trouble-free passes and be on your way. I estimate your chance of success in this at 90%.
The Immigration office offers no firm answers or help. You only know what can happen when you apply for something and either get approved or denied. You also get a glimpse in here by people who are living the problems but even for us there are no guarantees of anything. My overall advice to you is just come, work on problems as they arise, if any!