They invariably ask for passport info at some point, so you cannot use that dodge. Furthermore other info is available. The excuse that they must charge " all foreigners" the same is a crock. Pretty easy to differentiate resident expats from 30 day actual tourists on the basis of passport info, e.g. a number of consecutive non-immigrant renewals offers a clue. It would require a bit of programming, however, which Thai authorities seem reluctant to pay for qualified IT folks, e.g. the ongoing problems with 90 day reporting on line. I have done it a couple of times now, so it works, but there are still a couple of items that cannot be entered that show on the form.