Frontier 2012 have front blinkers invisible from side.

Don't know about the 2012 but my 2005 has signals on the corner. I think they are just a 194 bulb which is only a single filament so it can either burn steady or blink but not both. To make the bulb flash with your front signals, you would need to splice the positive wire from the light you WANT to flash into the positive wire from the light that DOES flash. I'm sure you could trace the circuit all the way back to the connector and make the splice there but, the easiest way would be to make the splice closer to the lights. If you decide to go this route, do a good job and do it once. Use solder butt connections and weather seal heat shrink and the repair will last the life of the truck. Using anything else -- wire taps, scotch locks, unsealed butt connectors or even the heat shrink type butt connectors are all cheap and easy but will eventually corrode and fail and cause you more headaches than you saved by taking the "easy" way. -- Good luck.