Looking for a plot where the main characters secretly get married and have to keep it quiet.  Not a contract marriage but they run off to get married and have to live quietly.

I'm not sure if this is what you're looking but,

Mudokono! (he is a pop idol and gets married, but has to hide his marriage from the media and his fans) 
Loving, Never Forgetting 

Its a C - Drama though with 34 episodes and I think they get married somewhere around episode18-20 .
not sure on this one but, the first ep of Emergency Couple has flashback to couple secretly getting married but married life doesn't last long, the rest of the drama though has them as ex's who end up at the same job as interns at a hospital and find their way back to each other.

My Secret Hotel, has lead couple having been previously married out of country with no guests or family, but they are ex's now and meet by chance when male lead is getting married again and female lead is wedding planner it's funny and cute and they have to find a way back to each other.

Neither of these really fits for living quietly, most of the time the family finds out and stirs the drama pot

Anymore suggestion? Im looking for a secret marriage that at some point, everyone knew they are actually married.  At the beginning, no one know if they are dating or even married. 

Secret Marriage that are actually marriage contract (due to some issue) and not everyone knows. So these are more like secret marriage contracts:

  • Khun Chai puttipat
  • Marriage contract 
  • Sunny Happiness 

Siren, if i remember, they are two cops who work together and they are secretly married