We (couple + 9 y.o. boy) have 5-6 nights in late July between SIN-KUL. Looking for a beach destination within 2-3h flight max between our stay in SIN and KUL.

Accommodation budget is U$100-200/night. Looking mostly beach and pool, but would enjoy a place with good food, interesting culture. Don't need a hellish "kids club" style places, just places which would welcome a well-behaved chid. Bali could fit the bill, but too chaotic? Phuket? Langkawi, Koh Samui, Perhentians, Vietnam...?

All ideas welcome!