Having a Thai bank account is totally irrelevant to Thai tax liabilities.
1) re the OP question: As soon as you have been 180 days within one calendar year in Thailand you become tax resident. Nothing more, nothing less.
2) re bank account and taxes: You (can) become tax liable, among other, when you bring foreign *income* into Thailand. Doesn’t matter how you bring it in. Can bring it in by bank transfer from a foreign account or can bring it in by carrying it on a mule when crossing the border. Having a (Thai) bank account is relevant to your tax liability.
We have Facebook SIG on Thai Tax Rules with 1700+ members and a few expert users (Thai tax lawyers).
Find the group here: Thailand Tax rules for expats
We have a SIG where we detail the fiscal consequences of moving (money) to Thailand. While I am merely the admin, and have some knowledge on the subject, we have a number of users like Pete Power here, and a few Thai tax lawyers, who are quite deep into specifics on the subject.
We do not discuss visa requirements and such. The group is strictly limited to factual discussions about the tax laws.
You can find the group here (click):
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PS: Basically, if you have earned 800,000 baht taxable income in 2025 it might be taxable. Most expats don’t earn that much foreign taxable income in less than six months.