Thy vs Thine

You'll find the use of thy and thine, as second-person singular pronouns in the King James Bible. Below is a simple explanation of when they are used.

Thy is a singular pronoun.
It is used before a noun that begins with a consonant or consonant sound.

Psalm 104:24 O LORD, how manifold are thy works! in wisdom hast thou made them all: the earth is full of thy riches.

Psalm 104:29 Thou hidest thy face, they are troubled:

Psalm 104:30 Thou sendest forth thy spirit, they are created:

Thine is also a singular pronoun.
It is used before a noun that begins with a vowel or vowel sound.

Psalm 104:28 ...thou openest thine hand, they are filled with good.

Psalm 110:1 Sit thou at my right hand, until I make thine enemies thy footstool.

Finally, here are a few verses that contain the use of both thy and thine. Notice the first letter of the first word occurring after the use of thy or thine.

Psalm 103:3 Who forgiveth all thine iniquities; who healeth all thy diseases;

Psalm 106:5 That I may see the good of thy chosen, that I may rejoice in the gladness of thy nation, that I may glory with thine inheritance.

Psalm 119:91 They continue this day according to thine ordinances: for all are thy servants.