What is "Bas Tzor"?
Radak: It is the congregation of Tzor, like "Bas Tziyon" (Melachim II, 19:21), "Bas Edom" (Eichah 4:21). Tzor is close to Eretz Yisrael, and will constantly bring a Minchah to each of the king's wives.
Whom does the verse address?
Radak: It says to each of the Bnos Melachim that the congregation of Tzor will always bring a gift to you.
Malbim: After discussing the king's honor, it describes how he goes from his ivory palace to his beloved's residence. There she stands with princesses; she is on the king's right. The author tells her to accept the law of Yisrael, and bow to the king, her master.
What is the meaning of "Yechalu"?
Rashi: It is [to seek,] like "va'Ychal Moshe" (Shemos 32:11). As a reward for this, those who are now rich will bring to you gifts.
What does the verse teach about "Ashirei Am"?
Radak: In addition to Bas Tzor, also the rich of every nation will seek your face.
Malbim: The rich of Tzor brought to Bas Tzor a dear gift, for her honor.
Malbim (Derech ha'Muskal): Dear royal garments are a metaphor for Chachmah, Musar and good Midos. They are a gift from the rich of Tzur the best powers of the Nefesh dependent on the body - Am Tzur.