My saga started with my signing up with a tax-filing agency. Said agency not only ignored my LTR status in their filing draft, but on top of that they wanted to file imaginary amounts that matched neither remittance nor dividends! After I decided I'd much better file myself, it was an uphill struggle to get that agency to hand over to me the password of my own eFiling account (loss of face you see). The long and the short of it is, I'm in no hurry to get involved with any (tax-filing or law) agency in TH ever again. In TH you "take a lawyer" and before you know it you find youself having to sue your lawyer.
As to the Royal decree being Law, yes it is but what Law are we talking about? With the help of a friend who is proficient in Thai, we endeavoured to find out what kind of income the Royal Decree is actually exempting (quite apart from the "following year" charade). Well guess what? It is as clear as mud. A world away from the blanket tax-exemption on foreign income/assets you see plastered all over the Internet. All it would have taken is for the Royal Decree to specify: "foreign income exempted" (with the possible caveat about the following year). It doesn't though, instead it waffles about "assessable income" and such like.