everything remitted is potentially taxable. If you have saving in a foreign bank, the principal can be brought in tax free but the interest which is earned after 1st jan 2024 is taxable. You must have documents to prove all statements.
"Only income remitted to Thailand is potentially taxable in Thailand, income that remains overseas is not taxable for tax residents." This is correct but there is a prososal being considered to extend this to gloabl income.
Not totally correct you have to read the detail of the DTA carefully, in most cases you get a credit for tax paid in the source country which can deduct from Thai tax.