165cm with 54kg is ok for female but for male i think its scrawny

yes very true bro. girls wouldnt want a guy smaller than them. your dating pool will be very limited.
glad u are married now and passed that zone. i was in a similar situation before but luckily situation improved once
i passed my uni age. started going to gym. bmi went up to around 21-22. now am married with kids but still wished my bmi was higher.
so recently been going back to exercise and bmi improved. almost reach my target of 25.
advice to other bros who wished to improve weight. remember its muscle u want to put on not weight. also gym is the best place.
if cant afford then youtube is a good source of information.
why go to gym when u can do at home? well gym u get to meet friends with similar goals and dedication. also u get support and encouragement.
at home you are not well equipped. also u will get lazy and give up eventually. another thing to remember is your diet.