Thanks everyone for the feedback. I'll enquire this afternoon with some of the other hotels close by. If no TM30 is forthcoming, I'll look for accommodation on the Bangkok side. (Although it sounds like if I go to the Bangkok immigration office, odds are no TM30 will be necessary ... maybe??)
So, the hotel should provide a TM30? Lesson learned. The taxi driver said that a lot of foreign laborers (Malaysians, Laotians, Cambodians, etc.) use this immigration office. Perhaps that's partly the reason for the more strict enforcement.