Family Travel - August - Singapore and??

Have booked flights to/from Singapore. Will be in South East Asia for three weeks (including the time in Singapore). Help me pick a destination(s) to add to Singapore. Looking to avoid monsoons/typhoons/heavy rain. Traveling with 15 yo teen son. We love a nice beach (but won’t be snorkeling or diving), interesting cities and towns, great food. I welcome all suggestions! Thank you!