Rashi (16, citing Yevamos 47b): Naomi had told her, Beis Din administers four death penalties.

Malbim: This is my purpose - to die the death of the straight, like you will. The Ru'ach will return to the bind of life.

Rashi (16, citing Yevamos 47b): Naomi had told her, there are two graveyards for those executed by Beis Din (for those who received lighter and harsher deaths).

Malbim: I want to be buried in Eretz ka'Kedoshah, in graves of Tzadikim prepared for rising at the revival.

Rashi: Like Hashem began doing evil to me, to kill my husband and make me lose my property - so He will increase if anything other than death separates between us.

Vilna Gaon: This is like Chazal said, even though the four Misos Beis Din ceased, the four Misos did not cease, and similarly in Gehinom. Even though the four Misos ceased in this world, there are deaths and afflictions in Gehinom like them for those who transgress His will. Do not tell me not to follow you due to punishments. The punishments are greater after death! Then, Hashem will punish me for my Aveiros here. Therefore, I want to convert and not to go away from you. This will save me from punishments in the world to come.

Malbim: She accepted a Shevu'ah that this is her primary purpose. I saw that death will make a great distinction between us. Even though in life I clung to you, even though creed separated us, love connected us. After death we will be separated. You will cling to Elokei ha'Ruchos, and I will be rejected, in the confines of idolaters. I want to convert, so also death will not separate us! Rus' words revealed that all foundations of Emunah of Hashem's existence and unity are proper in her heart - "your G-d is my G-d" (16). She believed in the eternity of the Nefesh, reward and punishment of the world to come and Techiyas ha'Mesim. Acquire Mitzvos and good deeds in this world, for you cannot in the world to come - death will separate between us!