600 Monk
A "600 monk" (or simply a "600") is a type of invincimonk who can have more than 55 HP. It is a common misconception that they need 600 or more health, but in reality they can work with nearly any amount. As with most invincimonks, this type of build is mostly used for farming. 600 monks make use of the skill Spirit Bond to stay alive. For this reason, they are sometimes called Spirit Bonders.
General Purpose
The general purpose of a 600 monk is farming for loot. Using Smiting Prayers to deal damage, the player can stay alive by using Protection Prayers Enchantments. These enchantments are commonly activation on hit, which means that the enchantments only activate when attacked. For self-healing and preservation, the only necessary skills are Protective Spirit and Spirit Bond.
Additional Skills
Using just two skills is ill-advised, even though it can be done. There are plenty of other skills that can aid in farming and make it more productive. Shield of Absorption, which was updated on 2006 October updates, is a common supplemental skill. During this update Spirit Bond was changed so it would only trigger the healing ten times instead of the enchantment wearing off. Shield of Absorption lets you fights many enemies at a time, while with Spirit Bond alone, you could only fight 8 to 5 creatures, depending on if you are in hard mode or not.
Energize
To maintain your energy you'll have to use either the Essence Bond or Balthazar's Spirit. This way every time you get hit, you also gain energy, thus never running out. To make these enchantments last longer you may want to equip Blessed Aura. If you mix Life Attunement with Spirit Bond you'll be healed for more and if you add Spell Breaker, you won't have to worry about your enchantments being removed for a time. One thing to remember is that interrupting spells and attack skills are the number one cause of death for 600 monks. To prevent this, add Mantra of Resolve or use Spell Breaker to counter spell interruptions.
Attack
Keeping yourself alive is one thing, but you also have to deal damage on your foes if you want the loot. This is where spells like Retribution come in, causing enemies that attack take in damage. Something else that can be used is Holy Wrath which combined with Retribution can really do serious harm to your attackers.
Aid
You may need a little help due to the effects that Holy Wrath can cause such as lose of energy. It's also helpful if your partner has some of the same skills and enchantments so that once your runs out, they can cast theirs on you.
Example
Below is an example of what your skill set might look like for a 600.