I’m married to my Thai wife and on an “0” Immigration visa transferring about 55,000 Baht per month for living expenses. Am I still liable for tax?

It depends on where the money is from. If it is income, for example, from investments, a pension or property rental, it is potentially taxable. If it is from savings from pre2024, it is not classified as a taxable asset and is not taxable. Depending on they jurisdiction for where your assets are based, there may be relief under a Double Tax Agreement using tax credits.