Sadly, the RAW answer is no. You can snipe and remain hidden, but your next attack is not a sneak attack because "stealthed" isn't a condition that makes a target flat-footed or denies it its Dex bonus to AC. Similarly, if you simply stay hidden until the battle is raging and try to shoot someone, it's not RAW a sneak attack. (It's not because it doesn't say it is, the rules are clear in omission.)
Of course this tends to defy reason, so I let people get in sneak attacks in other situations, as "it's the first round of a combat" is not a real in-game-world thing.
The devs understand the stealth rules are a big hot mess; in fact they posted some playtest new stealth rules on paizo.com in an attempt to come up with something less wonky.
Although it's neither feat nor psionic power, the effect you want's available as a low-priced magic item and a mid-level spell.
The Magic Item
The Web site Athas.org teeters on the extreme edge of official, saying that it
is recognized by WotC as the Official Dark Sun site on the internet. Content created on the official website is considered to be derivative work (as it is based on the intellectual property owned by Wizards of the Coast). This means that fan-created add-ons (such as new net books, adventures, etc.) are jointly owned by both Wizards of the Coast and the creator; neither can do anything outside the official website without the permission of the other. [sic]
Thus in the unlikely event the DM can be convinced to allow material from Athas.org (Comments' experiences say most DMs won't), the Athasian Emporium contains the
Third Eye Long Touch
The wearer of this kind of third eye [MIC 140] can use his touch attacks as if they were ranged touch attacks with a 30-foot range increment. It does not actually grant reach, and so does not help provide a flanking bonus or allow the wearer to make attacks of opportunity at any range greater than normal. The wearer uses his normal melee attack bonuses and normally affects the target with the effect of his touch if it hits, though the target of the attacks can benefit from cover or concealment.
Faint telekinesis; ML 1st; Craft Universal Item, far hand; Price 2,000 Cp.
The notation Cp--not to be confused with cp meaning copper pieces--stands for ceramic pieces, the Dark Sun campaign setting's equivalent to gold pieces. (Yes, in the Dark Sun campaign setting, the most commonly encountered currency isn't mined but baked. Just go with it.)
On the right face, this is a ridiculously useful item at a very low price.
The Spell
The 5th-level Sor/Wiz spell greater spectral hand [necro] (Dragon #303 36-7) is like the 2nd-level Sor/Wiz spell spectral hand [necro] (PH 282) except that "the hand can deliver any touch range spell of 6th-level or lower. In addition, if [the caster has] a supernatural effect tied to [his] touch, such as a paralyzing touch, the hand can deliver that effect as well." Further, the hand's 3d4 hp total is subtracted from the caster's own. (A non-greater yet still spectral hand has, instead, its 1d4 hp subtracted from its creator's hp.)
Just this far from fitting into a wand, one would have to cram the spell into a custom staff of greater spectral hand (34,050 gp; 4 lbs.) (50 charges) or talk to the DM about a different, even more custom magic item.
This is, admittedly, not a ranged touch attack and instead a means to use a touch attack at range, which may be close enough.
Best Answer
Ranged Touch Attacks Can Inflict Sneak Attack Damage
Although it's implied by the Player's Handbook, Complete Arcane clarifies this in the section Weaponlike Spells
A spell that requires a ranged touch attack require an attack roll. If the spell also deals damage, it can inflict sneak attack damage if sneak attack's conditions are met.
Further,
Thus, for example, the Rog1/Wiz3 who casts the 2nd-level Sor/Wiz spell scorching ray [evoc] (PH 274) can inflict with that spell an extra 1d6 points of fire damage by meeting the requirements for inflicting sneak attack damage, and, for example, a Rog3/Wiz7 who casts the 4th-level Sor/Wiz spell enervation [necro] (PH 226) can inflict with that spell an extra 2d6 points of negative energy damage by meeting the requirements for inflicting sneak attack damage.