I currently have a rebirth psychic samsaran who wants to have his soul "transcend".
Are there any good options, and I'm open to 3pp, for a transcended template?
Perhaps similar to a psychic lich, but without the inherent evil?
I am open to other thematic options as well.
For thematic reasons within Golarion, undead are almost universally evil.
The acts that go into Lichdom turn someone evil.
At this time, I'm not aware of anything that is equivalent without turning you evil.
You are basically asking for Baelnorn from Forgotten Realms.
The shabti from Pyramid of the Sky Pharoah might be similar to what you're considering. It's a race, not a template though.
This is a question for your GM. You're really not going to find much support for non-evil undead in Paizo's published material.
About the only non-evil undead you'll find in published Paizo material will be ghosts: the spirits of good people who died before they could accomplish something important, and that unfulfilled duty is keeping their spirits from moving to the Great Beyond. There are good-aligned ghosts that appear somewhere in Carrion Crown, Wrath of the Righteous, and Mummy's Mask, if I recall correctly. And there's a neutral ghost in Rise of the Runelords.
I think there might be a non-evil vampire somewhere in print, but I'm not positive of that.
That said, there are some options for transcending from a humanoid to an outsider. And there are other options for immortality (e.g. the sun orchid elixir).
From Wrath of the Righteons:
is a lich and after being imprisoned for 10,000 years he's willing to give it an "honest try" to redeeming himself if that's what it takes to secure freedom. So it's not *impossible* to redeem a lich ("honest try" to me suggests he's not just saying it), it's just that becoming a Lich turns you evil.
So a "non-evil Lich" is not necessarily a contradiction in terms in Golarion, it will just take exceptional circumstances.
More thematically appropriate for a Psychic is some sort of "you transcend to a higher form of existence and stop aging" but I'm not sure there's pre-existing mechanics for that.
There's a CG ghost in Undead Unleashed as well. But I'm not sure if there's a set way to become a ghost on purpose (and I doubt you'd be able to stay a PC after that). That'd mostly be GM discretion.
There is a mythic ability that gets you immortality, but that only helps if you're in a mythic game.
You could possibly try to "ascend" to being an outsider appropriate to your alignment, since people with particularly strong wills/etc. sometimes keep their sense of self/memories in the afterlife, but there aren't mechanics for that. It'd be up to your GM.
I mean, UMD can get you close for a price.
Scroll of contingency, scrolls of reincarnation (or clone), etc can really help you go a long way to never dying. Reincarnation works even if you die from old age.
I assume this is not for PFS, so:
You are talking about Transcendant Psychic, right?
Formless Adept
Source Occult Adventures pg. 104 (Amazon)
Formless adepts master their psychic powers to unshackle themselves from the confines of the flesh and empower their spellcasting. They learn to assume increasingly insubstantial forms until they become like living ghosts.
Phrenic Charisma: A formless adept uses his Charisma modifier to determine the number of points in his phrenic pool. This ability alters phrenic pool.
Formless Body: A formless adept gradually sheds his body, taking on increasingly nebulous forms. A formless adept can assume a formless body as a standard action. He can remain in each formless body type for a number of rounds per day equal to 3 + his Charisma modifier. The rounds don’t have to be used consecutively, but must be used in 1-round increments. Resuming his physical form takes another standard action; otherwise, the formless adept continues spending rounds of formless body until he runs out of them. The formless adept must return to his physical form before assuming a different formless body.
Blurred Body (Su): At 1st level, a formless adept can act under the effect of a blur spell. At 5th level, the formless adept can use this ability for a number of minutes per day instead of rounds per day. These minutes don’t have to be used consecutively, but must be used in 1-minute increments.
Gaseous Body (Su): At 5th level, a formless adept can become gaseous as gaseous form. At 13th level, the formless adept can use this ability for a number of minutes per day instead of rounds per day. These minutes don’t have to be used consecutively, but must be used in 1-minute increments.
Incorporeal Body (Su): At 13th level, a formless adept can become incorporeal (Pathfinder RPG Bestiary 301).
This ability replaces the psychic discipline and discipline powers class features.
Formless Spell: At 1st level, a formless adept gains the formless spell phrenic amplification. He can spend 1 point from his phrenic pool to cast a spell with a standard-action casting time as part of the action he uses to assume his formless body, expending the spell slot as normal. This ability replaces the 1st-level phrenic amplification.
Bonus Spells: The formless adept adds extra spells to his list of spells known while he’s in a formless body (including when he uses the formless spell phrenic amplification). Spells with a duration last for their full duration, even if the psychic reverts to his physical form. For feats and other abilities that require these spells as prerequisites, the psychic counts as knowing the spells but can benefit from the feats and abilities only while in a formless body. The formless adept gains the following spells at the appropriate levels: chill touch and expeditious retreat (1st), levitate and stricken heartACG (4th), gaseous form and vampiric touch (6th), shadow stepUM and telekinesis (8th), dominate person and synapse overload (10th), disintegrate and enemy hammerAPG (12th), finger of death and telekinetic sphere (14th), etherealness and power word stun (16th), and dominate monster and telekinetic storm (18th). This ability replaces discipline spells.
Psychic Possession (Su): At 15th level, while using his incorporeal body ability, a formless adept can attempt to psychically possess another living creature. To use this ability, the formless adept must be adjacent to the target. This effect works as the greater possession spell and can be maintained only as long as the formless adept maintains his incorporeal body form. The target can attempt a Will save with a DC equal to 10 + 1/2 the formless adept’s class level + the formless adept’s Intelligence modifier to resist the effect. A creature that successfully saves is immune to the formless adept’s psychic possession for 24 hours. This ability replaces the 15th-level phrenic amplification.
Formless Master (Su): At 20th level, a formless adept can assume any formless body as a swift action and change between formless body types as a standard action (without returning to his physical form first). He can use the formless spell phrenic amplification to cast any spell with a swiftaction casting time when assuming a formless body or any spell with a standard-action casting time while switching between formless bodies. The formless adept also adds his Charisma bonus as a deflection bonus to his AC while in a formless body. A formless adept can attempt a saving throw to bypass any spells that prevent entry of incorporeal creatures (such as anti-incorporeal shellACG), even if the spells don’t normally allow one. This ability replaces remade self.
Lichdom should be more of a Fall than a Transcending for a psychic, especially a Samsaran, as it would be denying the central belief core of the race, and probably end the character's cycle of rebirth.
If your character really is meaning to do that, it's dark, but Thematically sound.
I assume your GM is OK with the Ascension concept. Perhaps other templates might work better.
Wouldn't even a Celestial, Half Celestial or even Advanced template fit better for a Samsaran? Even going Fey seems closer to concept than going Undead.