If it's a Pro Raider, they started to make them in 1984.
Some say that the M4 in the serial means it's a 1984 but i'm not sure of that.
If it's not a Pro Raider, then you need to see to the details of the frame.
1987 Tai made, brakebridge engraved with Hutch almost the same font like the US made frames and serial on the dropouts also simular like the US version.
Later Tai models, from 1988 (or late 87), have a engraved brakebridge with more rounded font, same as the Pro Raider brake bridge and the serial on the BB.