Southeast Asian mainland: Burma (Myanmar), Cambodia, Laos, Thailand, Vietnam and Peninsular Malaysia
Southeast Asian islands and archipelagos: Brunei, East Malaysia, East Timor, Indonesia, Papua New Guinea, the Philippines, and Singapore
I've been to like half those countries. Of the ones I've been to, I would call Singapore the most successful of them based on any reasonable metric. The countries I haven't been to also aren't the ones you'd write home about - Laos, Burma, etc. So moral relativism and "well, okay, they're healthy, safe, prosperous, long lived, developed, international, and educated - but do they do what really matters?!" - yeah, I don't think that one applies here.
Singapore is hands down the cleanest, safest, overall nicest country in Southeast Asia. The people are friendly, polite, and courteous. Maybe a little bit too much deference to authority, but there's no any really creative hyper-individualistic societies anywhere else in SE Asia, and there are some interesting thinkers and researchers in Singapore anyways. There's also some decent culture and interesting things going on, excellent local cuisine, decent and friendly nightlife - it's pretty easy to make friends there, the culture is warm enough, and they've got the Confucian-descended ideals about taking care of your family and all that, which I quite respect and think is one of the biggest things missing from the West right now. Really, Singapore is a very nice and wonderful place.
One might also ask: Is the phenomenon being described here a necessary component of Singapore's success (however defined) or an ancillary one? And, even if it was necessary once, does it continue to be so?