The honest answer about Pattaya restaurant reservations: most places don't need them, and a handful of places will absolutely refuse you without one.
The 'don't need them' category covers most of the directory: casual Thai sit-downs, mid-priced internationals, neighbourhood Italian places, brunch cafes. Walk in any night before 19:30 and you'll get a table within ten minutes. After 19:30 on a Friday or Saturday in high season, expect a 15-minute wait at the better places.
The 'absolutely book ahead' category is short: the top three or four fine-dining destinations on Pratumnak Hill, the marquee weekend brunches at the major hotels, anything with a tasting menu, and any beachfront sunset table during November-February. For these, 24-72 hours' notice is the floor; a week ahead is safer for Saturday slots.
The middle category — places where reservations help but aren't required — is where most tourists trip themselves up. The five-star hotel restaurants, the better steakhouses, the rooftop spots. Book if you can, walk in if you can't, and either way the experience will be fine.