There’s a fantastic search engine called google. Guaranteed it’s covered at least 10 times.
You’d have your answer already and wouldn’t be waiting for Tod Daniels to answer this question for the Nth time. But don’t worry. There’s at least a dozen people that will weigh in with inaccurate, incomplete information and then you’ll get the official answer a bit later on today.
I agree with Tod and he’s the expert on these matters.
To share my experience for the past several years I would spend 6-7 months at a time in Thailand.
Come in visa exempt and then extend. Go to Laos for one night for SETV, then extend. Repeat trip to Laos for SETV, extend again if necessary. (I sure miss having the old double-entry.)
Never had an issue. Nary an eye or explanation. Never showed funds or onward tickets. Came to Thailand on one-way air tickets.
Your itinerary is perfectly acceptable and normal. It is that of a tourist to SE Asia. I’ve done the SE touring over the years and fell in love with Thailand which is why I did what I’d done.