Is it possible to stay in Thailand for 10 weeks and then 12 weeks across two trips with tourist visas?

It's great your trying to plan ahead , however the Thai immigration can change the 60 day visa exempt overnight back to 30 days so don't bank on the 60 day VOA.

So I'd personally be looking doing it correctly and get yourself a tourist visa for each entry.

When you say you will be on a 60 day tourist visa ,do you mean you will be applying for a 60 day visa or getting 60 day visa exemption on arrival, because there is a difference.

Your plan is generally doable, but there are two important details you need to be aware of regarding extensions. If you enter on visa exempt entries, Thailand now allows only one 30 day extension per calendar year. Any second extension in the same year will normally be limited to 7 days. Since your second stay crosses into 2027, the extension rules will probably reset on 1 January, but only if your second stay is under visa exemption. However, if you instead use tourist visas for both trips, most immigrations still issue 30 day extensions twice. That’s usually a slightly safer option when planning longer stays in the same year. Also keep in mind that everything ultimately depends on your total time spent in Thailand within a rolling period in the discretion of the IO you’re facing not just the calendar year. If your previous stays have not been excessive, you should be fine with the plan you’ve outlined. If your two trips were closer together, a 6-month METV would have been the sensible choice. But with such a long gap between visits and a proper return to your home country in between, both trips should be entirely feasible on either visa exemption entries or single-entry tourist visas provided you have a clean previous entry history.