Move to Provence, Olover :-)

No law has changed. The 15-day visa on arrival has been in place for 6 years or so. Whoever told you differently was probably misinformed. The strange thing is that you got your VOA despite the fact that your outbound ticket is for a month after your arrival. Yes, you can try leave and return for another VOA (just make sure you don't come back 15 minutes after your departure), but it's entirely up to the Immigration staff if they grant it or not. Anyway, this being your first trip to Thailand and your overall stay not exceeding 1 month, I think you'll be OK.