instead of paying $20 to $35 for a handyman to change the lock, i bought a cam lock from the shop opposite Sim Lim Tower. It costs me $2. Homefix sells their for $3.50 and also one for $36!
Just a adjustable spanner to unlock the nut holding the lockset and fit in the new lock. But the moving plate is too long so I just bent it to the correct length. Took me less than 15 mins.