im looking for drama where ml dies or disappears and then comes back with a different identity

Hua Jai Sila

Bai Mai Tee Plid Plew (ML becomes transgender, so you'd be watching a female actress) 

The Last Empress 

A Man in a Veil (daily drama, still airing right now. There are 100 episodes 30 minutes each but the ML is good at acting his character. He becomes a prosecutor/starts getting revenge after the first 20 episodes) 

Man from the Equator

• The Devil/Lucifer
• Green Rose
• Money Flower
• Cruel City
• Pinocchio
• When the Devil calls your name
• Temptation of an angel
• Goodbye Mr. Black - sadly i dropped this one

None korean:

• Nirvana in Fire
• Maou - japanese remake of Lucifer
• The Count of Monte-Cristo: Great Revenge

ML is born in Korea but "disappears" to be raised in America and returns with an American name and nobody recognizes him from the past:

• Her Private Life
• Mr. Sunshine

The regime exiled him and tried to kill him and he came back as a rebel vigilante:

• The Princess's Man

Prince gets amnesia from an injury during an attempted assassination, goes missing, and takes on the identity of a poor villager:

• 100 Days My Prince

I forget the exact details. ML was a prince and was believed to be dead but returns and the FL isn't sure whether or not its him at first:

• Queen for Seven Days

General sort of dies, sort of gets cursed and becomes a Goblin / King dies and becomes a Grim Reaper:

• Goblin

Not Korean:

• The Untamed - China
• When I See You Again - Taiwan 

Abyss - he dies and comes back with completely different and new look