@Pete *****
If you become a full-time resident of Thailand, you're no longer a resident of NYS and do NOT have to pay NYS tax (you may eventually be asked to prove that you live in Thailand, but as long as you can have bills/statements in your name sent to you, and provide a copy of your passport stamps and Visa/renewals, you will be fine).
Evidence of using a Thai bank account, and using a credit card within Thailand is also good evidence of being a resident of Thailand, as well as receipts from medical appointments, etc.
And yes, I still keep a mailing address in NYS (with a relative).
You can also still be registered to vote in NY, but don't vote in any local (city/state) elections, or that will be considered as evidence towards residence in NYS.