Re: Malaysia and Thailand
u cant cover much in a day in singapore. as mehnazq said, though its small, there's much to explore. depending on ur interests i guess. u can either explore chinatown, little india, orchard etc and shop at da same time or u can just stick to places of interests such as sentosa. night safari etc. btw dun be shy to experiment local food.
and honestly, local neighbourhoods such as geylang bazaar or bedok town are so much more interesting and cheaper than tourist spots.
as for malaysia, the city of kuala lumpur is very much like singapore. u can get more info with ur hotel reception to visit other states such as malacca, langkawi, tioman, penang etc
shopping is definitely cheaper in malaysia.