If the turn light comes on but just doesn't flash then yes it could be one of the 3 turn signal bulbs is burned out on that side
If the other side works then Flasher is OK
Also for 1990, 1994 and earlier, try 4-way flasher to test if bulb is burned out, it uses a different flasher but all 6 bulbs
If the bulb is not coming on then its either burned out or has lost 12v or ground, which can be in the multi-function switch
Front and dash bulbs use different Grounds, but share the 12v
Diagram here:
https://therangerstation.com/tech_library/EDiagrams/files/Diagram_turn_stop_hazard.JPG
In the turn signal stalk(multi-function switch) the front and dash turn signal bulbs are power by 1 wire and the rear is powered by another wire
So if that 1 wire or contact inside switch is bad then front and dash bulbs would be out, wouldn't come on at all
4-ways use a different power path inside the switch but share the 1 wire out to that sides front and dash bulbs
So if the 4-ways work for all 6 bulbs then the problem is the contact in the multi-function switch for the turn signal on that side
If front and dash bulbs are still not on with 4-ways, then problem can be that 1 wire or also the multi-function switch