In most countries, if you stay longer than 180 days you are considered resident for tax purposes. Your visa is not relevant. The current position is you would be assessed for tax on money you bring in to Thailand. But you can deduct any tax already paid in the source country, so maybe no more tax is payable. Government sources say Thai Revenue is now discussing a plan to tax all income worldwide, even if it is not brought into Thailand.
You're proving again it is exactly about your white privilege, Nigel. Those who have fled terror are refugees and entitled to sanctuary where they apply for it. Those who have not will be returned. Government determines spending. This one has managed to run up a record debts while slashing public spending and persuading idiots like you it's the fault of refugees. But the truth is you just don't like foreigners, otherwise you'd accept these simple facts instead of believing trash fascist newspapers