you have to set boundaries. collectively Singaporeans are bad at pushing back. one of my ex bosses once said, if you say yes to some request over a weekend once, people will assume it's ok for you to work on weekends and keep expecting it from you all the time. so you have to push back.

i had another ex boss who had a strict policy of no working on weekends, when you're sick, and when you're on leave.

even my current boss now expects me to push back on unproductive work.

i think the trick is to work for ang mo bosses? i started doing that many years back out of necessity due to my health problems i needed better work life balance. Ang mo bosses tend to focus on the most important tasks at hand. SG bosses will give you an avalanche of stuff to do like too many ppts and meetings you don't need to attend. And they generally do not respect your time, cos they operate out of fear of authority and their desire to be in authority's good books.