As established in an FAQ a long while ago, you can take weapon focus and improved critical (ray).
1: If you take Mythic Improved Critical, does the ray spell deal triple damage?
2: Can you take weapon focus and improved critical for melee touch attacks or non-ray ranged touch attacks?
1) Yes, Weapon Focus (Ray) is an actual feat you can take, and Improved Critical (Ray) as well. There's an FAQ that confirms this. and Another FAQ. Mythic Improved Critical will affect whatever chosen weapon you have Improved Critical with, so Imp Crit (Ray)--> Mythic Imp Crit (Ray) = Kosher.
Improved Critical (Mythic)
Your critical strikes with your chosen weapon are deadlier than most.
Prerequisite(s): Improved Critical, base attack bonus +8.
Benefit: Your critical multiplier with your chosen weapon is increased by 1 (to a maximum of ×6).
Special: You can gain this feat multiple times. The effects do not stack. Each time you take this feat, it applies to a different non-mythic Improved Critical feat.
2) RAW I don't believe you can, and I don't think there's an FAQ that clears this up either. But tbh, I don't see any reason why you couldn't, given that Weapon Focus (Ray) and (Bomb) and (Unarmed Strike) exist, it's not far fetched or unbalancing that Weapon Focus (Touch) could be a thing, in my opinion.
The reasoning behind this is that Rays are considered Weapons, and conversely, even though you're considered "armed" and don't provoke AoO's, Touch Attacks not a weapon. So your GM is entirely within the rules to say "No" to Weapon Focus (Touch).
Maybe bribe your DM with weekly footrubs and the occasional bag of snacks or pudding 6-pack.
