Here is the Moveset I have on my Alolan Raich
Item: Focus Sash
Ability: Surge Surfer
EVs:252 Sp.A, 252 Speed, 4 Hp
Modest Nature (+Sp.A, -Atk)
-Hidden Power (Ice)
Electric Terrain, Helps Raichu in so many ways and angles. Not only does it power up its Thunderbolt, but it also doubles your speed. Pokemon that out speed may now be much slower than you and thats when you go for a massive hit on the Pokemon. Focus sash also allows it to survive a single turn to set up that electric terrain and attack afterwards. However raichu is vulnerable to priority moves like a simple bullet punch from a metagross or a lucario or even a multi hit move from Alolan Marowak and etc.
Thunderbolt Gains STAB, Electric Terrain boost, and just great power in all.
Hidden Power (Ice), Great Coverage against ground, grass, or dragon types who want to resist you.
Psychic, STAB and coverage
Things to look for: Alolan Marowak is a HUGE threat to this Pokemon. Not only does it have a ground multi-hit move, but all your moves have either no effect cuz of marowak's lighting rod or resistance. Also you may want to look out for Pokemon that usually have priority moves like lycanroc or Mimikyu that can knock you out right after your focus sash is used.